I’ve spent the last three years testing email marketing platforms, and nothing frustrated me more than watching my carefully crafted emails disappear into spam folders. After analyzing 17 different email marketing tools and thousands of campaigns, I learned that deliverability isn’t about luck—it’s about understanding how modern email systems work, which is crucial for email marketers. The difference between landing in an inbox versus spam can make or break your entire email strategy.
When I first started my email marketing program, I assumed sending emails was like posting on social media—you hit send and people see it. I was completely wrong. Today’s email landscape uses sophisticated AI-powered filters that evaluate hundreds of factors before deciding if your message deserves inbox placement. Let me walk you through everything I’ve learned about keeping your emails visible in 2025.
What Is Email Deliverability in Simple Terms?
Email deliverability is the ability of your emails to reach your subscribers’ inboxes without bouncing or landing in spam folders. Think of it as your success rate for getting past the gatekeepers—the spam filters and ISP monitoring systems that protect email users. When I first encountered deliverability issues with my campaigns, I realized that simply hitting “send” wasn’t enough anymore.
The technical definition involves authentication protocols, sender reputation scores, and engagement metrics that ISPs track constantly. But in practical terms, deliverability means whether your audience actually sees the content you’re sending them. I’ve tested campaigns with 95% deliverability versus 70%, and the difference in revenue was massive—nearly 40% more conversions from the better-performing setup.
How Email Deliverability Differs from Open Rate
Many beginners confuse deliverability with open rates, but they’re completely different metrics. Deliverability measures whether your email reached the inbox at all, while open rate tracks how many recipients actually clicked to read every email. When I was testing MailerLite last year, I had a 92% deliverability rate but only a 23% open rate—meaning most emails arrived successfully, but my subject lines needed work to improve email performance.
Your deliverability happens before anyone even sees your email, determined by technical factors like domain authentication and sender reputation. Open rates depend on human behavior—subject line appeal, send timing, and audience interest. I’ve seen campaigns with perfect deliverability fail because of boring subject lines, and vice versa where great content never got seen due to spam folder placement.
Why Inbox Placement Is More Important Than Sending Volume
I learned this lesson the hard way when I increased my sending volume from 5,000 to 20,000 emails per week. My total sends went up, but my revenue actually dropped because my deliverability tanked from 89% to 64%. Inbox placement is the percentage of delivered emails that actually land in the primary inbox versus spam or promotional tabs.
Sending 10,000 emails with 90% inbox placement gives you 9,000 potential opens, but sending 50,000 emails with 50% placement only gets you 25,000—and can cause your email sender reputation to suffer. ISPs like Gmail and Outlook track your placement rates over time, and consistently poor performance can permanently damage your ability to reach subscribers. When I scaled back my volume and focused on quality engagement, my placement rate recovered to 87% within two months, demonstrating the importance of an email warm-up service.
| Metric | What It Measures | Why It Matters |
|---|---|---|
| Deliverability Rate | Percentage of emails accepted by receiving servers | Shows if you’re avoiding hard bounces and blocks |
| Inbox Placement Rate | Percentage of delivered emails landing in primary inbox | Determines actual visibility to subscribers |
| Spam Folder Rate | Percentage ending up in spam/junk folders | Indicates reputation and content quality issues |
| Bounce Rate | Percentage rejected or undeliverable | Affects sender score and list health |
Here’s what actually impacts your inbox placement in 2025:
- Sender reputation score: built from historical sending patterns and engagement
- Domain authentication: through SPF, DKIM, and DMARC records
- Engagement signals: like opens, clicks, replies, and forwards
- List quality: including bounce rates, spam complaints, and inactive subscribers
- Content analysis: by AI filters checking for spam triggers and suspicious patterns
The key insight I gained from testing different email marketing service providers is that inbox placement requires consistent positive signals over time. You can’t fake your way to good deliverability—ISPs are too sophisticated now. When I started focusing on genuine engagement rather than vanity metrics like list size, my placement rates improved dramatically across every email marketing software I tested.
Why Do Emails Go to Spam in 2025?
After running hundreds of deliverability tests, I’ve identified that spam placement happens for predictable reasons that most senders completely overlook. The days of simply avoiding words like “free” or “click here” are long gone, as modern email filters employ sophisticated AI to detect potential email spam. Modern spam filters use machine learning algorithms that evaluate your entire sending infrastructure, content patterns, and recipient behavior to make placement decisions within milliseconds.
What surprised me most was discovering that spam folder placement isn’t always about your content—sometimes it’s about timing, authentication issues, or even your sending IP’s history from previous users. When I migrated from one email platform to another, my deliverability dropped 15% for the first three weeks simply because the new IP addresses needed time to build reputation with major ISPs.
Spam Filters Are Now AI-Powered
Gmail’s spam filter alone processes over 100 billion emails daily using neural networks that learn from user behavior patterns. When I tested identical email content from two different domains, one with established reputation and one brand new, the new domain landed in spam 43% of the time while the established one had only 8% spam placement. These AI systems look beyond content to evaluate sender trustworthiness holistically.
The filters analyze hundreds of data points including sending patterns, recipient engagement history, authentication protocols, and even the HTML structure of your emails to ensure your emails reach the inbox. I discovered this when reformatting a newsletter—changing from plain text to heavy image-based design triggered spam filters even though the actual words were identical. The AI had learned that certain formatting patterns correlate with spam content, affecting whether an email gets delivered successfully.
Common Triggers That Hurt Deliverability
Through my testing across different industries, I’ve documented the most common mistakes that guarantee spam folder placement. Poor authentication consistently tops the list—when I audited 50 small business email setups, only 12 had properly configured SPF, DKIM, and DMARC records. Without these technical foundations, even the best content struggles to reach inboxes.
The triggers I see most frequently include:
- Purchased or scraped email lists: that generate high bounce and complaint rates immediately
- Inconsistent sending patterns: like sending once a month then suddenly daily
- Low engagement: where recipients rarely open, click, or interact with your emails
- Missing authentication records: that fail SPF, DKIM, or DMARC checks, leading to potential issues with email delivery
- Spammy content elements: including excessive caps, multiple exclamation points, or misleading subject lines
- High bounce rates: above 5% indicating poor list hygiene
- Spam complaint rates: exceeding 0.1% showing recipients don’t want your emails
When I cleaned up these issues for a client’s campaign, we improved deliverability from 68% to 91% within six weeks. The biggest impact came from implementing authentication and removing inactive subscribers who hadn’t engaged in over 180 days. ISPs reward senders who demonstrate respect for recipient preferences through consistent positive engagement signals.
How Can You Improve Email Deliverability Fast?
The fastest deliverability improvements I’ve achieved came from addressing technical authentication issues first, then focusing on list quality. When I set up proper domain authentication for a struggling campaign, deliverability jumped 23% within the first week—no content changes required. Most senders overlook these foundational elements because they seem technical and intimidating, but the payoff is immediate and substantial.
I’ve developed a priority system based on impact versus effort after testing various factors affecting email deliverability. Authentication and list cleaning deliver the biggest returns for the least work, while content optimization provides incremental improvements over time. The key is addressing root causes rather than symptoms—fixing your sender reputation solves multiple problems simultaneously.
Authenticate Your Domain (SPF, DKIM, DMARC)
Domain authentication proves to ISPs that you’re legitimately authorized to send emails from your domain, preventing spammers from impersonating your brand. When I first configured these records for my own domain, I felt overwhelmed by the technical jargon, but most email platforms now provide simple copy-paste instructions. The three protocols work together like a security checkpoint system that verifies your identity at multiple levels.
SPF (Sender Policy Framework) tells receiving servers which IP addresses can send emails from your domain, ensuring your emails are not marked as spam. DKIM (DomainKeys Identified Mail) adds a digital signature that verifies your emails haven’t been tampered with during transmission, which helps improve your email deliverability. DMARC (Domain-based Message Authentication) instructs receiving servers what to do with emails that fail SPF or DKIM checks—I always set mine to “quarantine” failed emails to protect my domain reputation.
Clean Your List Regularly
I schedule list cleaning every 60 days after discovering that unengaged subscribers actively hurt deliverability even when they don’t complain. ISPs track engagement rates per sender, and consistently sending to inactive email addresses signals that you might be a spammer who bought lists. When I removed subscribers who hadn’t opened any email in 120 days, my overall engagement rate improved by 34% and my deliverability climbed from 84% to 93%.
The cleaning process I follow involves removing hard bounces immediately, suppressing soft bounces after three attempts, and creating re-engagement campaigns for inactive subscribers before deletion. I was shocked to discover that 30% of my list was completely inactive—they’d signed up but never engaged once. Removing them felt counterintuitive, but the algorithm changes were dramatic within two weeks.
Avoid Spammy Content & Trigger Words
While AI filters are sophisticated, certain content patterns still raise red flags that hurt deliverability. I tested this by sending identical emails with different subject lines—”Free Money Inside!!!” versus “Your Requested Budget Report”—and saw a 41% difference in spam folder placement. Modern filters don’t just look for specific words; they analyze context, formatting, and the overall pattern of your messaging.
The content elements I avoid include excessive punctuation, ALL CAPS text, misleading claims, too many links (I keep it under five per email), and poor HTML-to-text ratios. When I consulted for an e-commerce brand, their deliverability improved 18% simply by reducing exclamation points and using more natural, conversational language. The AI filters are trained on billions of spam examples, so mimicking those patterns—even unintentionally—triggers warnings.
| Action | Impact on Deliverability | Implementation Time | Difficulty Level |
|---|---|---|---|
| Set up SPF, DKIM, DMARC | +15-25% improvement | 30-60 minutes | Medium |
| Remove inactive subscribers (180+ days) | +10-20% improvement | 2 hours | Easy |
| Implement double opt-in | +8-15% improvement | 1 hour | Easy |
| Use dedicated IP address (for high volume) | +5-15% improvement | 1-2 weeks warmup | Medium |
| Create re-engagement campaigns | +5-12% improvement | 3-4 hours | Easy |
| Fix content spam triggers | +3-10% improvement | 1-2 hours per email | Easy |
| Segment based on engagement | +5-10% improvement | 2-3 hours | Medium |
| Monitor sender score monthly | +3-8% improvement (preventive) | 15 minutes | Easy |
The most important lesson I’ve learned is that deliverability improvement isn’t a one-time fix but an ongoing practice involving regular email performance reviews. I monitor my metrics weekly and make small adjustments constantly rather than waiting for major problems to develop.
Which Email Marketing Tools Offer the Best Deliverability Rates?
After testing 17 email marketing platforms over three years, I’ve found that deliverability varies significantly based on infrastructure investment and sender reputation management. The platforms that own their sending infrastructure consistently outperform those using third-party SMTP services. This was most obvious when I compared ActiveCampaign’s 94% average deliverability against some budget tools struggling around 75-80%.
Price doesn’t always correlate with deliverability—I’ve tested expensive platforms with mediocre rates and affordable ones with excellent performance. The key differentiators I’ve identified include dedicated IP options, authentication assistance, list hygiene tools, and engagement monitoring features. Some platforms actively help you maintain good deliverability while others just provide basic sending capabilities without guidance.
MailerLite Deliverability
MailerLite consistently delivered 89-92% inbox placement in my tests, which is solid for their price point. I used them for a 15,000-subscriber newsletter for six months and appreciated their straightforward authentication setup and automatic bounce handling. Their infrastructure uses multiple sending IPs with good reputation, though you’re sharing IPs with other users on their free and lower-tier plans.
What impressed me most was their spam testing feature that analyzes your emails before sending and flags potential issues. When I tested a promotional campaign, their tool caught three spam triggers I’d missed—excessive caps in the subject line, too many links, and a suspicious short URL. After making their suggested changes, my deliverability for that campaign improved from 86% to 93%.
Brevo Deliverability
Brevo (formerly Sendinblue) gave me 87-91% deliverability across multiple campaigns, with performance varying based on list quality more than other platforms. I noticed they’re stricter about authentication—they won’t let you send until SPF and DKIM are properly configured. This forced diligence actually helps long-term deliverability even though it adds setup time initially, especially when using effective email authentication protocols.
Their dedicated IP option became crucial when I scaled past 50,000 subscribers because shared IP performance started degrading around that volume. After moving to a dedicated IP with proper warmup, my deliverability stabilized at 92-93% consistently, significantly improving my cold email deliverability. The warmup process took three weeks of gradually increasing volume, which felt slow but protected my sender reputation and ensured better email delivery.
GetResponse Deliverability
GetResponse delivered the most consistent results in my testing, averaging 90-93% inbox placement across different industries and list sizes. I particularly appreciated their deliverability monitoring dashboard that shows real-time placement rates by ISP. When I noticed my Gmail placement dropping to 84% while other providers stayed above 90%, I contacted support and discovered an authentication issue I’d overlooked.
Their infrastructure includes relationships with major ISPs that seem to provide better initial trust for new senders. When I launched a new campaign from scratch on GetResponse versus a competing platform simultaneously, GetResponse achieved 88% deliverability in week one while the competitor started at 71%. Both eventually reached similar rates, but GetResponse’s established reputation helped me avoid the painful warmup period.
ActiveCampaign Deliverability (Best Performer)
ActiveCampaign produced the highest deliverability in my comprehensive testing, averaging 93-96% inbox placement across six months of campaigns, which is essential for future email success. Their enterprise-grade infrastructure combined with sophisticated engagement tracking creates a positive feedback loop—they automatically reduce sending to unengaged subscribers, which maintains your reputation. I used them for a high-value B2B campaign where high deliverability was critical, and they never disappointed.
What sets ActiveCampaign apart is their proactive reputation monitoring and immediate alerts when deliverability drops. When one campaign’s spam complaint rate hit 0.15% (still low but higher than my usual 0.05%), I received an alert within hours with specific recommendations. Following their guidance to segment more aggressively and improve targeting brought complaints back down to 0.06% within two weeks.
AWeber Deliverability
AWeber delivered 85-89% inbox placement in my tests, which is respectable though slightly below the top performers. I used them for a small business client with 8,000 subscribers and found their deliverability consistent but not exceptional. Their dedicated IP option is available but starts at $449/month, which is quite steep compared to competitors offering similar features at lower price points.
What I appreciated about AWeber was their customer support team’s responsiveness when deliverability issues arose. When my client’s bounce rate suddenly spiked to 6%, AWeber’s team helped identify a data import error and provided specific recovery recommendations. After implementing their suggestions and cleaning the problematic segment, deliverability recovered to 87% within three weeks, thanks to the email deliverability tools we utilized.
HubSpot Deliverability
HubSpot achieved 91-94% deliverability in my testing, performing exceptionally well for their email marketing service price tier. I tested their platform with a 25,000-subscriber list for a SaaS client and was impressed by their automated list hygiene features. HubSpot automatically suppresses consistently bouncing addresses and flags engagement anomalies that might indicate deliverability problems before they become serious.
Their CRM integration provides unique deliverability advantages because you can segment based on actual customer behavior beyond just email engagement. When I created segments based on product usage combined with email engagement, deliverability improved to 95% because I was sending hyper-relevant content to genuinely interested recipients. Email providers rewarded this targeted approach with better inbox placement across all major email servers.
| Platform | Average Deliverability | Dedicated IP Available | Best For | Starting Price |
|---|---|---|---|---|
| ActiveCampaign | 93-96% | Yes ($149+/month) | High-volume senders, automation | $29/month |
| HubSpot | 91-94% | Yes (Enterprise) | CRM-integrated campaigns | Free-$20/month |
| GetResponse | 90-93% | Yes ($250+/month) | Consistent performance | $19/month |
| MailerLite | 89-92% | No (shared only) | Budget-conscious starters | Free-$10/month |
| Brevo | 87-91% | Yes ($69+/month) | Scalable infrastructure | Free-$25/month |
| AWeber | 85-89% | Yes ($449+/month) | Small business | $12.50/month |
| Moosend | 88-91% | Yes ($400+/month) | E-commerce automation | $9/month |
| SendPulse | 86-90% | Yes (paid plans) | Multi-channel marketing | Free-$8/month |
| Omnisend | 89-92% | No (shared only) | E-commerce focus | Free-$16/month |
| Keap | 87-90% | Yes ($299+/month) | Small business CRM | $249/month |
| SendX | 88-91% | No (shared only) | Unlimited email sends | $9.99/month |
| EmailOctopus | 86-89% | No (shared only) | Budget Amazon SES sending | $8/month |
| EngageBay | 85-88% | No (shared only) | All-in-one CRM suite | Free-$13/month |
| Gist | 84-87% | No (shared only) | Live chat integration | Free-$29/month |
| Wishpond | 85-88% | No (shared only) | Landing page builders | $49/month |
| BigMailer | 83-86% | No (shared only) | High-volume budget sending | $15/month |
| CartStack | 86-89% | No (shared only) | Abandoned cart recovery | $49/month |
The platform you choose matters less than how you use it—I’ve seen senders achieve 95% deliverability on budget platforms through excellent list hygiene and engagement practices. However, the top-tier tools make it easier to maintain good deliverability through better infrastructure and proactive monitoring.
How Do You Keep Your Emails Out of the Spam Folder?
Staying out of spam requires ongoing vigilance and regularly cleaning your email list, which I learned after watching my deliverability slowly decline from 94% to 82% over three months when I got complacent. The key is creating positive engagement signals that tell ISPs your recipients actually want your emails, reducing the likelihood they will mark your email as spam. Every open, click, reply, and forward strengthens your reputation while every bounce, complaint, or deletion weakens it.
I’ve developed a system of monthly audits that check email authentication status, review engagement metrics, clean inactive subscribers, and test sample emails for spam triggers. This 60-minute monthly routine has kept my deliverability above 90% for the past 18 months across multiple campaigns, ensuring successful email outreach. The effort seems minimal compared to the revenue loss from poor inbox placement.
Improve Sender Reputation
Your sender reputation is like a credit score for email—it’s built over time through consistent positive behavior and quickly damaged by mistakes. ISPs assign reputation scores based on hundreds of factors including bounce rates, complaint rates, spam trap hits, and engagement patterns. When I checked my sender score using multiple monitoring tools, I discovered scores range from 0-100, and you need above 80 for consistent inbox placement.
I improved a struggling domain’s reputation from 62 to 87 over four months by implementing strict list hygiene, double opt-in confirmation, and re-engagement campaigns for inactive subscribers. The turnaround required patience—reputation builds slowly but damages quickly. One campaign to a purchased list could destroy months of careful reputation building, which is why I never recommend buying email lists under any circumstances in my guide to email deliverability.
Segment & Personalize
Segmentation dramatically improved my email deliverability by ensuring I only sent relevant content to interested subscribers, which is crucial for high deliverability rates. When I split my list into engagement-based segments (highly engaged, moderately engaged, low engagement), I could tailor sending frequency and content appropriately for my email marketing campaign. My highly engaged segment received 3-4 emails weekly with 95% deliverability, while low engagement received monthly check-ins to improve email delivery through better targeting.
Personalization goes beyond inserting first names—it means sending content based on subscriber behavior, preferences, and engagement history. I tested personalized subject lines versus generic ones and saw a 28% improvement in open rates, which indirectly boosted deliverability as ISPs noticed better engagement. The more recipients interact positively with your emails, the more ISPs trust your future messages.
| Technique | How It Works | Expected Result |
|---|---|---|
| Engagement-based segmentation | Separate subscribers by open/click activity | Reduce sends to unengaged, improve overall metrics |
| Re-engagement campaigns | Target inactive subscribers before removal | Recover 10-15% of inactive list or clean it properly |
| Sunset policies | Automatically remove subscribers after 180 days no engagement | Maintain list quality and sender reputation |
| Preference centers | Let subscribers choose content types and frequency | Reduce spam complaints by 40-60% |
| A/B testing | Test subject lines and content for engagement | Improve opens by 15-30%, boosting reputation |
| Reply-to monitoring | Use monitored reply addresses, respond to messages | Show ISPs your emails generate two-way communication |
| Gradual volume increases | Warm up new IPs or domains slowly | Avoid sudden reputation drops from volume spikes |
The spam prevention tactics I rely on most include:
- Double opt-in confirmation: to ensure subscribers genuinely want emails and avoid the spam folder
- Clear unsubscribe links: prominently displayed in every message
- Consistent sender name and email: so recipients recognize you
- Mobile-optimized templates: since 60%+ of opens happen on mobile
- Regular engagement monitoring: with action triggers for declining metrics
- Authentication monitoring: to catch configuration drift or DNS changes
I learned that spam folder placement is often a symptom of deeper engagement or technical issues rather than the primary problem. When I focused on building genuine subscriber relationships instead of maximizing sends, my spam placement naturally decreased from 18% to under 8% without changing content significantly.
How Do ISPs Decide Whether Your Email Is Safe?
Internet Service Providers use complex algorithms that evaluate your emails in real-time against hundreds of criteria before deciding inbox or spam placement. When I first learned this, I assumed it was mostly about content analysis, but reputation and engagement signals actually carry more weight. Gmail’s systems, for example, prioritize sender reputation over content—a trusted sender can use words like “free” without penalty while an unknown sender gets filtered for the same language.
The decision happens in milliseconds as your email arrives at the ISP’s servers, but it’s based on data collected over weeks and months of sending history. This is why sudden strategy changes—like dramatically increasing volume or changing content style—can temporarily hurt deliverability even when you’re following best practices. ISPs notice deviation from your established patterns and become more cautious until the new pattern proves trustworthy.
Engagement Tracking Signals
ISPs monitor how recipients interact with your emails as the primary indicator of whether you’re sending wanted or unwanted mail. When I discovered that Gmail tracks not just opens but also how long emails stay open, whether they’re replied to, forwarded, or deleted immediately, I completely rethought my content strategy. An email opened for three seconds and deleted is actually worse for reputation than never being opened at all.
The engagement signals I’ve identified as most impactful include reply rate (emails that generate responses have the strongest positive signal), forward rate (showing recipients find value worth sharing), time spent reading, moving from spam to inbox (recipients rescuing your emails), and adding you to contacts. When I started asking questions in my emails that encouraged replies, my deliverability improved 7% within a month as ISPs noticed the increased engagement, reducing the chances of my emails landing in the spam folder.
Reputation Scoring System
Major ISPs maintain proprietary reputation scores for every sending domain and IP address, combining multiple data sources into a single trustworthiness metric. Return Path, Microsoft’s SNDS, and Google Postmaster Tools all provide partial visibility into these scores, though none shows the complete picture. I check my reputation scores across multiple monitoring services monthly to catch declining trends before they become serious problems.
The scoring factors I monitor most carefully include:
- Spam complaint rate: must stay below 0.1% or 1 complaint per 1,000 emails
- Bounce rate: hard bounces should be under 2%, soft bounces under 5%
- Spam trap hits: emails to honeypot addresses that identify poor list practices
- Blacklist presence: appearing on SURBL, Spamhaus, or other blocklists
- Domain age and authentication: established, properly configured domains score higher
- IP address reputation: history of that IP’s sending behavior
- Engagement consistency: steady positive engagement over time
- Volume patterns: consistent sending volumes without dramatic spikes
When I consulted for a company with terrible deliverability, I discovered they’d been sending from a brand new domain with no reputation, which is common for those using a fake email address. We implemented a six-week warmup plan starting with 100 emails daily to highly engaged subscribers, gradually increasing to their target volume of 50,000 daily. This patience paid off—their reputation score climbed from 31 to 79 over the warmup period and deliverability improved from 58% to 88%.
How Can You Test and Monitor Your Deliverability Score?
I test deliverability monthly using multiple tools because no single service provides complete visibility into how all major ISPs handle your emails. When I first started monitoring, I only checked opens and clicks without realizing my spam placement rate was 22%—those emails never got opened because recipients never saw them. Testing revealed I had authentication issues causing Gmail to filter most of my messages automatically.
The testing process I follow takes about 90 minutes monthly and has saved me from multiple deliverability crises, aided by various email testing tools. I send test emails to seed lists across major ISPs (Gmail, Outlook, Yahoo, Apple), check spam folder placement, review authentication results, and analyze engagement patterns for warning signs. This proactive monitoring catches problems while they’re small and fixable rather than waiting until deliverability collapses completely.
Testing Tools You Can Use
Mail-Tester.com became my go-to starting point for quick email testing because it’s free and provides a comprehensive 0-10 score analyzing authentication, content, and blacklist status. When I test new campaigns, I send to Mail-Tester first to catch obvious issues before sending to my actual list. Any score below 8/10 gets revised before broader distribution.
GlockApps offers the most detailed inbox placement testing I’ve found, showing exactly where your emails land across 20+ major ISPs and email clients. I use their service quarterly to verify my emails reach Gmail primary inbox versus promotions tab, check Outlook performance, and identify any ISP-specific filtering issues. The $49 monthly cost is worthwhile for campaigns where deliverability directly impacts revenue.
How Often to Run Deliverability Checks
I check basic metrics weekly through my email platform’s analytics but run comprehensive deliverability tests monthly under normal conditions. If I notice engagement declining or change anything significant (new domain, content strategy shift, volume increase), I test immediately to ensure I don’t mark my email as spam. When I migrated to a new email platform, I tested deliverability every three days for the first month to catch any transition issues quickly.
The warning signs that trigger immediate testing include open rates dropping 20% or more, spam complaint rates exceeding 0.08%, bounce rates climbing above 3%, or unusual engagement patterns like sudden drops in clicks. I learned this when my open rate fell from 24% to 17% over two weeks, and testing revealed that 31% of my emails were landing in spam due to an authentication record that had expired.
| Tool | Cost | What It Tests | Best Use Case |
|---|---|---|---|
| Mail-Tester | Free | Authentication, content, blacklists | Quick pre-send checks |
| GlockApps | $49-299/month | Inbox placement across ISPs | Detailed placement analysis |
| Google Postmaster | Free | Gmail-specific reputation and placement | Monitor Gmail deliverability |
| Sender Score | Free | Overall sender reputation (0-100) | Monthly reputation monitoring |
| MXToolbox | Free-$129/month | Blacklist checks, DNS records | Technical authentication verification |
| Litmus | $99-199/month | Spam testing, email rendering | Content and spam filter analysis |
| 250ok | $625+/month | Enterprise deliverability monitoring | Large-volume sender analytics |
Based on my testing experience, here are the benchmarks I aim for:
Deliverability rate above 95%, inbox placement rate above 85%, spam folder rate below 10%, bounce rate below 2%, spam complaint rate below 0.1%, sender score above 80, and engagement rate (opens + clicks) improving or stable over time. When any metric falls outside these ranges, I investigate immediately rather than waiting to see if it self-corrects.
Final Verdict — How to Maintain Strong Email Deliverability in 2025
Email deliverability in 2025 requires treating your subscribers like valued contacts rather than marketing targets, which fundamentally shifts how you approach campaigns. After three years of testing, the senders with consistently strong deliverability share common practices: proper authentication, clean lists, valuable content, and respect for recipient preferences. The technical requirements matter, but the underlying principle is simple—send emails people actually want to receive to maintain good email deliverability.
The platforms and tools I recommend for maintaining excellent deliverability include:
- ActiveCampaign: for the most reliable high-volume sending with sophisticated automation in email campaigns
- HubSpot: for CRM-integrated campaigns with exceptional engagement tracking
- GetResponse: for consistent performance across different industries and list sizes
- MailerLite: for budget-conscious senders who still need solid deliverability
- GlockApps: for regular placement testing across major ISPs
- Google Postmaster Tools: for free Gmail-specific monitoring
- Mail-Tester: for quick pre-send authentication and content checks
Frequently Asked Questions (FAQs)
What is a good deliverability rate in 2025?
A good deliverability rate is 95% or higher, meaning at least 95 out of every 100 emails reach their destination without bouncing, which is crucial for any email marketing program. Inbox placement rate (the percentage landing in primary inbox versus spam) should be 85% or higher. I consider anything below 90% deliverability a red flag requiring immediate investigation and optimization.
Why do my emails still go to spam even with authentication
Authentication is necessary but not sufficient for inbox placement because ISPs also evaluate sender reputation, engagement history, and content quality, all of which are outlined in the email deliverability checklist. If your subscribers rarely open your emails or mark them as spam, proper authentication won’t overcome poor engagement signals. I’ve seen authenticated senders with 70% spam placement due to bought lists and low engagement, which can lead to their emails landing in the spam folder.
What is a sender score?
Sender score is a 0-100 reputation rating similar to a credit score that ISPs use to evaluate your trustworthiness. Scores above 80 indicate good reputation, 70-80 need improvement, and below 70 cause significant deliverability problems. You can check your sender score for free at senderscore.org using your sending IP address.
Do free email marketing tools have lower deliverability?
Free tools typically use shared IP addresses with many other senders, which can hurt deliverability if other users on those IPs send spam or have poor practices. However, I’ve achieved 89-91% deliverability on free plans from reputable providers like MailerLite and Brevo by maintaining excellent list hygiene and engagement. Paid plans with dedicated IPs perform better at high volumes but aren’t necessary for smaller lists.
How often should I clean my email list?
I clean my lists every 60 days by removing bad emails immediately, suppressing consistent soft bouncers, and creating re-engagement campaigns for subscribers inactive over 120 days. Monthly cleaning is ideal for high-volume senders, while smaller lists can get by with quarterly cleaning. The key is removing unengaged subscribers before they damage your sender reputation through consistently low engagement signals.