How to Improve Email Deliverability (Actionable Guide)
What Email Deliverability Actually Means (and Why It's Declining)
Email deliverability is the percentage of your emails that reach the inbox — not the spam folder, not the promotions tab, not the void. It's different from your "delivery rate," which only measures whether the email was accepted by the receiving server. An email can be "delivered" and still end up in spam. Deliverability is about inbox placement specifically. According to EmailToolTester's ongoing deliverability tests across major email marketing platforms, the average deliverability rate is 83.1%. That means roughly 1 in 6 marketing emails either lands in spam or disappears entirely. For some platforms, the number is worse — the lowest performer in their tests (Benchmark) hit just 47.1%. Deliverability has also gotten harder in the last two years. In February 2024, Google and Yahoo began enforcing stricter authentication requirements for bulk senders. In May 2025, Microsoft followed with its own enforcement for Outlook and Hotmail. In September 2025, La Poste (France's major email provider) added similar rules. The direction is clear: inbox providers are raising the bar, and senders who don't meet the new standards will see their emails filtered out. The good news: most deliverability problems are fixable. They come from a few specific, addressable issues — missing authentication, dirty lists, poor sending patterns, or platform choice. This guide covers each one with specific steps you can take this week.
Step 1: Set Up Email Authentication (SPF, DKIM, DMARC)
Email authentication is no longer optional. As of 2026, Gmail, Yahoo, Outlook, and several other providers require proper authentication for bulk senders. Without it, your emails will be filtered or rejected outright. There are three protocols you need to set up, and they work together: **SPF (Sender Policy Framework)** tells receiving servers which systems are authorized to send email from your domain. It's a DNS record that lists your approved sending sources — your email marketing platform, your transactional email service, your business email provider. How to set it up: Add a TXT record to your domain's DNS. Your email marketing platform will give you the exact record to add. Most platforms (MailerLite, Klaviyo, Brevo, etc.) include this in their onboarding setup guides. One critical rule: SPF has a 10-DNS-lookup limit. Every "include" statement in your SPF record counts toward this limit. If you use multiple email services (marketing platform + transactional email + CRM + helpdesk), you can easily exceed it. When the limit is exceeded, the entire SPF record fails — and inbox providers treat your emails as unauthenticated. **DKIM (DomainKeys Identified Mail)** adds a digital signature to your emails that proves they haven't been tampered with and actually came from your domain. It uses cryptographic keys — a private key on your sending server signs the email, and a public key in your DNS lets the receiver verify it. How to set it up: Your email platform generates the DKIM keys. You add the public key as a DNS record (usually a CNAME or TXT record). Every major email platform walks you through this during setup. Common mistake: Using your email platform's default DKIM signing instead of setting up custom signing with your own domain. Default signing means the DKIM signature shows the platform's domain, not yours — which causes alignment failures with DMARC. **DMARC (Domain-based Message Authentication, Reporting, and Conformance)** ties SPF and DKIM together. It tells inbox providers what to do when an email fails authentication (nothing, quarantine it, or reject it) and sends you reports about who's sending email using your domain. How to set it up: Start with a permissive policy: `v=DMARC1; p=none; rua=mailto:dmarc@yourdomain.com`. This monitors without blocking anything. Collect reports for 2–4 weeks, fix any authentication failures you find, then gradually tighten the policy to `p=quarantine` and eventually `p=reject`. Don't skip straight to `p=reject`. If you have authentication gaps (a forgotten sending system, a misconfigured SPF record), a reject policy will cause legitimate emails to bounce.
Step 2: Clean Your List (and Keep It Clean)
Dirty lists are the second most common cause of deliverability problems after missing authentication. Inbox providers monitor your engagement rates — if a large percentage of your recipients never open or click, that signals low-quality sending, and your reputation drops. **What "dirty" looks like:** - Contacts who haven't opened an email in 6+ months - Email addresses that hard bounce (the address doesn't exist) - Spam trap addresses (recycled old addresses that inbox providers use to catch senders with poor list hygiene) - Purchased or scraped email lists (never do this — it's the fastest path to blacklisting) **Immediate cleanup steps:** 1. Remove all hard bounces. Every platform does this automatically, but verify it's happening. 2. Segment out contacts who haven't engaged in 90 days. Send them a re-engagement campaign ("Do you still want to hear from us?"). If they don't respond within 2–3 emails, remove them. 3. Check for obvious junk: addresses like test@test.com, misspelled domains (gmial.com instead of gmail.com), role addresses (info@, admin@, sales@) that tend to be unmonitored. **Ongoing hygiene practices:** - Use double opt-in for new subscribers. Yes, it reduces your signup rate by 20–30%. But it dramatically improves list quality because every address is verified as real and active. - Set up a sunset policy: automatically suppress or remove contacts who haven't engaged in a defined period (90 days for ecommerce, 6 months for newsletter-type lists). This is the single most impactful ongoing practice for deliverability. - Run your list through an email verification service (like ZeroBounce, NeverBounce, or BriteVerify) annually, or before any major campaign to a segment you haven't emailed recently.
Step 3: Warm Up New Domains and IPs Properly
If you're sending from a new domain, a new email platform, or a new dedicated IP address, you can't send 50,000 emails on day one. Inbox providers will flag sudden high-volume sending from an unknown source as spam. **Domain warm-up protocol:** Start with 100–500 emails per day during the first week. Increase volume by 15–20% each week. At this rate, it takes roughly 6–8 weeks to reach full sending capacity. During warm-up, send only to your most engaged subscribers — people who have recently opened or clicked. Their positive engagement signals (opening, clicking, not marking as spam) build your sender reputation. If you send to cold, unengaged contacts during warm-up, the negative signals (no opens, spam reports) can tank your reputation before it's established. **When warm-up is necessary:** - You've registered a new sending domain - You've switched email marketing platforms - You've been assigned a new dedicated IP address - You haven't sent any emails in 30+ days **When warm-up is not necessary:** - You're on a shared IP (most small-to-mid-size senders) and switching between platforms that use shared infrastructure - You're increasing send volume gradually as your list grows organically **Shared vs. dedicated IPs:** Most email platforms put smaller senders on shared IP addresses, meaning your reputation is pooled with other senders on the same server. This is usually fine — reputable platforms actively monitor and remove bad senders from shared IPs. Platforms like MailerLite and ActiveCampaign maintain particularly clean shared IP pools, which is part of why their deliverability scores are consistently high. Dedicated IPs are available from most platforms once you reach higher sending volumes (typically 50,000+ emails/month). They give you full control of your sender reputation — which is great if your list is clean and engaged, but can backfire if your list quality is poor, because there's no one else's good reputation to balance out your bad signals.
Step 4: Write Emails That Inbox Providers (and People) Actually Want
Authentication and list hygiene get your emails to the inbox. What you write determines whether they stay there. Inbox providers — especially Gmail — increasingly use engagement-based filtering. If recipients consistently ignore, delete, or mark your emails as spam, future emails get filtered regardless of your authentication setup. Conversely, if people open, click, reply, and move your emails to their primary inbox, you build positive reputation. **Content practices that protect deliverability:** Avoid spam trigger patterns. This doesn't mean avoiding the word "free" (that myth died years ago). It means avoiding the patterns that spam filters actually flag: ALL CAPS subject lines, excessive exclamation marks, image-only emails with no text, misleading subject lines, and emails with a poor text-to-link ratio (too many links relative to body text). Keep your complaint rate below 0.1%. Google explicitly states that senders should maintain a spam complaint rate under 0.1%, and absolutely under 0.3%. At 10,000 sends, that means fewer than 10 spam reports. Every spam complaint hurts, so always include a visible, working unsubscribe link (legally required anyway under CAN-SPAM and GDPR), and don't make it hard to find. Include a plain-text version. Most email platforms generate this automatically, but verify it's enabled. Some inbox providers check for a plain-text alternative as a spam signal. Send consistently. Erratic sending patterns — nothing for two months, then three campaigns in one week — confuse inbox providers. A regular cadence (weekly, biweekly, whatever fits your content) keeps your reputation stable. **The engagement feedback loop:** When someone opens your email, it tells Gmail (and others) "this sender is wanted." When they click a link, that signal is even stronger. When they reply, that's the strongest signal of all. Some marketers deliberately include reply prompts ("Hit reply and let me know...") specifically because replies improve sender reputation. It works, but only if the prompt is genuine — fake engagement bait can backfire with savvy subscribers.
Platform Deliverability: How Your Email Tool Affects Inbox Placement
Your email marketing platform has a direct impact on your deliverability, and the differences between platforms are larger than most people realize. EmailToolTester has been running bimonthly deliverability tests across major platforms since 2015. Their methodology sends identical emails to real accounts across Gmail, Outlook, Yahoo, and other providers, then measures what percentage reaches the inbox. **Latest deliverability rankings (EmailToolTester, most recent five rounds averaged):** Top tier (89%+ — Excellent): - ActiveCampaign: 94.2% — Reclaimed the #1 position. Consistently strong across Gmail and Outlook. - MailerLite: 94.41% (five-round average) — Earned the "best of 5" award for sustained performance. - GetResponse: 90.9% - Brevo: ~89.1% Mid tier (83–88% — Acceptable): - Mailchimp: ~88% - AWeber: 83.1% Below average (under 83%): - Omnisend: 75.1% **Why platforms differ:** Deliverability comes down to IP reputation, infrastructure, and enforcement. Platforms that aggressively police their sender base — rejecting signups that look spammy, suspending accounts with high complaint rates, investing in dedicated deliverability teams — maintain better shared IP reputations. MailerLite's strict approval process, for example, is annoying when you're trying to get started, but it's directly linked to their deliverability performance. By filtering out questionable senders before they can damage shared IP reputation, everyone on the platform benefits. **What this means for you:** Choosing a high-deliverability platform gives you a starting advantage, but it's not the whole picture. A sender with perfect authentication, a clean list, and engaging content on Omnisend will outperform a sender with sloppy list hygiene on ActiveCampaign. Platform choice sets the floor; your practices determine where you actually land. That said, if deliverability is your top concern — and for some industries like finance, healthcare, and B2B it absolutely should be — ActiveCampaign and MailerLite are the safest bets right now.
A Deliverability Checklist You Can Use Today
Here's a condensed action plan. Work through it in order — each step builds on the previous one. **This week:** - [ ] Verify SPF, DKIM, and DMARC are configured for your sending domain. Use a tool like MXToolbox or your email platform's built-in authentication checker. - [ ] Set your DMARC policy to `p=none` with reporting enabled if you haven't already. Review reports in 2–4 weeks. - [ ] Remove all hard bounces from your list (most platforms do this automatically — verify). - [ ] Archive or remove contacts who haven't opened or clicked in 6+ months. **This month:** - [ ] Implement double opt-in for all new subscribers. - [ ] Create a re-engagement campaign for inactive subscribers (90+ days without engagement). Suppress those who don't respond. - [ ] Set up a sunset policy: automatically suppress contacts after a defined inactivity period. - [ ] Review your email content for spam trigger patterns: check your text-to-image ratio, link density, and subject line formatting. **This quarter:** - [ ] Move your DMARC policy from `p=none` to `p=quarantine` after confirming all legitimate senders pass authentication. - [ ] Consider BIMI (Brand Indicators for Message Identification) setup — it displays your verified brand logo next to your emails in supported inboxes. Adoption is growing in 2026. - [ ] Run a full list verification through a service like ZeroBounce or NeverBounce. - [ ] Monitor your deliverability using tools like GlockApps, Inbox Placement by Litmus, or your platform's built-in deliverability dashboard. **Ongoing:** - [ ] Keep spam complaint rate below 0.1%. - [ ] Send on a consistent schedule. - [ ] Continuously segment and suppress unengaged contacts. - [ ] Review deliverability metrics monthly, not just open rates. Deliverability isn't a one-time fix. It's a set of ongoing practices that compound over time. The businesses that consistently land in the inbox are the ones that treat list quality and authentication as maintenance tasks, not projects with an end date.
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