How to improve your email deliverability

To improve email deliverability, fix the signals every mailbox provider rewards: authenticate every message with SPF, DKIM, and an enforced DMARC policy; mail only people who opted in and keep your list clean; earn engagement through relevant, segmented sends; warm up new domains and IPs gradually; and keep your spam complaint rate under 0.1% and hard bounces under 2%. Do those consistently and inbox placement follows.

There is no single switch that fixes deliverability, and no trick that beats good behavior over time. What works is a short list of fundamentals applied in the right order. This guide ranks them by impact so you spend your effort where it moves the needle, then shows you how to measure the result and diagnose a slide before it costs you the inbox.

Deliverability vs delivery: the difference that decides the inbox

Delivery means the receiving server accepted your message. Deliverability means it landed in the inbox rather than spam. A message can be delivered and still never be seen, which is why a 99% delivery rate can hide a real inbox problem.

When your sending platform reports a high delivery rate, it is telling you the recipient's server did not reject or bounce the message. It says nothing about where the message went next. The provider still routes accepted mail to the inbox, the spam folder, or a quiet promotions tab based on your reputation and the recipient's behavior. Inbox placement is the metric that actually matters, and it is almost always lower than your delivery rate suggests.

So when people ask how to improve deliverability, the real goal is inbox placement: more of your accepted mail reaching the primary inbox. Everything in this guide bends that number upward.

The five pillars of inbox placement

Inbox placement rests on five pillars: authentication, reputation, list quality, engagement, and infrastructure. Mailbox providers weigh all five on every send, and a weakness in any one can drag the others down.

No single pillar wins on its own. Perfect authentication will not save a list full of people who never asked for your mail, and a beautifully segmented campaign still fails if your sending IP has no reverse DNS. The providers add the signals up, so you have to tend all five.

Reputation is the connective tissue here. It is the running judgment each provider forms from your authentication, your list, and how recipients react. For a deeper look at how that score is built and recovered, read what sender reputation is.

The deliverability playbook, in priority order

Work these five steps in order. The first two prevent most spam-folder problems outright, and the rest steadily lift you from acceptable to excellent inbox placement.

How to warm up a new domain or IP

Warming up means raising volume in measured steps so each provider can learn that your mail is wanted. A typical ramp runs two to four weeks, beginning with your most engaged subscribers and only growing when the metrics stay healthy.

The schedule below is a sensible starting point for a new domain or dedicated IP. Treat it as a ceiling, not a quota: if bounces or complaints climb at any stage, hold volume steady until they settle before stepping up again.

The numbers that define healthy sending in 2026

Mailbox providers publish hard limits, and crossing them gets you filtered or rejected. Keep spam complaints under 0.1%, hard bounces under 2%, and treat the 2024 bulk-sender rules as the baseline, not a goal.

These are the thresholds that matter most right now:

• Spam complaints under 0.1%. That is one complaint per thousand delivered messages. Gmail reports your complaint rate in its postmaster tool and treats 0.3% as a hard ceiling that triggers filtering, so 0.1% gives you headroom.
• Hard bounces under 2%. A higher rate signals poor list hygiene. Suppress every hard bounce immediately so you never mail a dead address twice.
• Full authentication for bulk senders. Since February 2024, anyone sending roughly 5,000 or more messages a day to Gmail and Yahoo accounts must pass SPF and DKIM, publish an aligned DMARC policy, and offer one-click unsubscribe through the List-Unsubscribe header. Microsoft applied the same expectation to high-volume senders to its consumer inboxes in May 2025, and now rejects non-compliant bulk mail outright.
• Matching reverse DNS. Every sending IP should have a PTR record whose hostname resolves back to that IP. Missing or mismatched reverse DNS is an instant trust penalty.
• Steady volume. Predictable cadence beats spikes. A sudden tenfold jump reads like a compromised account and invites throttling.

Signals that help vs hurt deliverability

Almost every deliverability factor has a good version that builds trust and a bad version that erodes it. The table below pairs them so you can audit your program line by line.

How to measure your deliverability

You cannot improve what you do not watch. Track four numbers, inbox placement, bounce rate, complaint rate, and engagement, and read them together rather than in isolation.

Each metric tells part of the story, and the gaps between them are where problems hide. A healthy delivery rate with falling engagement, for example, often means more of your mail is quietly being routed to spam.

• Inbox placement rate. The share of accepted mail that reaches the primary inbox rather than spam or a low-priority tab. Industry averages sit near 84%, so roughly one in six emails miss the inbox. Aim for 90% or higher; 85% is acceptable, and anything below 70% needs urgent attention.
• Bounce rate. The percentage of messages rejected as undeliverable. Keep hard bounces under 2% and investigate any sudden rise, which usually points to a bad import or stale segment. Our bounce rate guide breaks down soft versus hard bounces.
• Complaint rate. The share of recipients who mark you as spam. Stay under 0.1% and read it straight from Google Postmaster Tools and Yahoo and Microsoft feedback loops, which report complaints back to you.
• Engagement. Opens, clicks, and replies over time. Treat open rate as a trend rather than an absolute, since privacy features inflate it, and weight clicks and replies more heavily because they are harder to fake.

The fastest place to start is a free reputation check, which grades your authentication, blacklist status, and DNS from A to F in one pass and hands you specific fixes.

Why are my emails going to spam?

If mail you used to land is now going to spam, something measurable changed. Work through the usual suspects in order, because the most common causes are also the fastest to fix.

1. Broken or missing authentication. A DNS edit, a new sending tool, or an expired DKIM key can break alignment overnight. Re-check SPF, DKIM, and DMARC first, since a single failure can sink an otherwise healthy program.
2. A complaint spike. One irrelevant or unexpected campaign can push complaints past the threshold. Pull back to your most engaged recipients and tighten relevance before sending broadly again.
3. A bad list import. Adding old, purchased, or unconsented addresses raises bounces and trap hits at once. Remove the suspect segment and suppress every bounce.
4. A new blacklisting. A trap hit or a compromised account can land your domain or IP on a blacklist, dropping placement sharply. Scan with the Blacklist Checker and follow the delisting steps.
5. A volume spike or gap. A sudden surge, or a long silence followed by a blast, reads as risky. Return to a steady cadence and re-warm if you have been quiet for weeks.
6. Slipping engagement. When opens and clicks fall, providers infer your mail is unwanted and start filtering it. Prune dead weight and re-earn attention with relevant, segmented content.