Email deliverability checklist: 12 checks before you send

An email deliverability checklist is the set of checks that gets your mail accepted by Google, Yahoo, and Microsoft, which now enforce published requirements at the door instead of filtering after the fact. This one has 12 checks in four groups, and the first five decide whether your mail is accepted at all.

Fail a provider's requirements and the message doesn't get filtered, it gets rejected. The checklist below covers what Google, Yahoo, and Microsoft require, plus the operational work that keeps you clear of their limits once you're compliant.

Key takeaways

• An email deliverability checklist has 12 checks in four groups: five on authentication, four on infrastructure and testing, three on consent and list hygiene. Work them in that order, because authentication failures block mail outright.
• Google applies its bulk sender rules at 5,000 messages a day to Gmail accounts. Microsoft applies its high-volume rules at 5,000 or more messages to its consumer services, counted per From domain.
• SPF, DKIM, and DMARC are required by all three providers. Passing one is no longer enough.
• Google and Yahoo both cap spam complaints at 0.3%. Yahoo gives you two days to honor an unsubscribe.

What does an email deliverability checklist cover?

An email deliverability checklist covers four things: the authentication records that prove you are who you claim to be, the infrastructure that carries your volume, the exit paths you give consumers, and the list hygiene that keeps complaints below the enforced ceiling. Skip any one group and the other three won't save you.

Twelve checks fit in those groups. Five are authentication, four are infrastructure and testing, and three cover consent and hygiene. Work them in that order, because authentication failures block mail outright while hygiene problems degrade you gradually.

What affects email deliverability most?

Authentication affects email deliverability more than any other factor, because it's evaluated before content, reputation, or engagement enter the picture. Microsoft rejects mail from domains that fail authentication with a 550 5.7.515 error and the message "Access denied, sending domain does not meet the required authentication level." No amount of list quality recovers from that. Our marketer's guide to email authentication covers how each record works; the checks below are what to verify.

1. SPF. Publish an SPF record listing every service that sends on your behalf. Google, Yahoo, and Microsoft all require it.
2. DKIM. Sign your mail. All three providers require DKIM, and Yahoo's sender best practices specify that bulk senders implement both SPF and DKIM rather than choosing one.
3. DMARC with alignment. Publish a DMARC record at a minimum policy of p=none (monitor only, no enforcement). The harder part is alignment: the domain in your From header has to match the SPF or DKIM domain. Microsoft states that "the SPF and/or DKIM record (at least one) must align with the domain in the 5322.From address" (the From address your reader sees). A record that exists but doesn't align still fails.
4. TLS. Confirm your platform sends over TLS; Google's sender guidelines require it. This is usually a platform setting rather than something you configure per campaign, so confirm it rather than assume it.
5. Forward and reverse DNS. Verify forward and reverse DNS for every sending IP. Google and Yahoo require it for all senders, and Microsoft's Outlook.com sender support page says it "may not accept email from senders who fail a reverse-DNS lookup." Reverse DNS is the check most often missing after an infrastructure change.

BIMI sits one step past the requirements: it puts your logo in the inbox, and it only works once DMARC is at enforcement.

How do you check email deliverability before a send?

Checking email deliverability before a send means verifying that your infrastructure is sized for the volume and testing where mail actually lands, rather than confirming it was accepted. Acceptance and inbox placement are different outcomes, and standard reporting only shows you the first one.

1. Sending IP capacity. Review your number of sending IPs against daily and monthly volume. Acoustic's deliverability team recommends one IP address for every two million messages per day to avoid delivery delay. A dedicated IP also needs steady volume: below roughly 100,000 emails a month, it probably won't build enough reputation signal for mailbox providers to evaluate, and that volume is what decides whether a dedicated or shared IP fits your program.
2. Subdomain segmentation. Separate subdomains for separate streams. Marketing and transactional mail shouldn't share a reputation, because a promotional campaign that draws complaints shouldn't be able to delay a password reset.
3. Warming. Introduce new IPs and new sending domains slowly. Volume that appears from nowhere reads as a compromised host. Ramp schedules vary with your monthly volume and how engaged your earliest sends are, so build the curve around your own list rather than a generic calendar.
4. Seed and placement testing. Send to a seed list across the major providers and confirm where messages land, not just that they were accepted. Then break opens and clicks down by recipient domain. A 3% open rate at one provider against 20% at another points to a placement problem at the low one. Read those numbers carefully: Apple Mail Privacy Protection inflates opens, so lean on the email metrics worth tracking beyond open rate. Google's Postmaster Tools gives you the reputation dashboard for Gmail specifically.

What is a good email deliverability rate?

A good email deliverability rate keeps your spam complaint rate below 0.3%, the ceiling Google and Yahoo enforce, and ideally below Google's own 0.10% target; providers publish pass-fail limits, not an industry benchmark. The table below lists what each provider states publicly. Where a provider hasn't published something, the cell says so rather than borrowing a number from somewhere else. Comparing the three providers side by side is a different job from getting ready for the Gmail and Yahoo sending requirements step by step.

Read the complaint rate row carefully. Google's own target is below 0.10%, and 0.30% is the level it tells senders to avoid ever reaching. Sitting just below the ceiling leaves no room for a single bad send, and complaint rate reacts faster than any other signal on this list. Acoustic recommends keeping your spam complaint rate at 0.2% or below, which leaves room for a bad send before you reach the limit.

How do you improve email deliverability that's already slipping?

Improving email deliverability that's already slipping starts with reducing the volume you send to people who aren't reading, because inactive recipients drive both the complaints and the spam trap hits (sends to addresses providers seed to catch stale lists) that caused the decline. Yahoo states it directly: sending to users who aren't reading your messages "will harm your delivery metrics and reputation."

1. One-click unsubscribe. Add a List-Unsubscribe header with List-Unsubscribe-Post for one-click; Google and Yahoo both require it, and Yahoo gives you two days to honor the request. This is a header, not a footer link: a visible link in the body is still expected but doesn't satisfy the rule on its own, and an easy unsubscribe protects sender reputation (https://www.acoustic.com/resources/blog/easy-unsubscribes-protect-sender-reputation) well beyond compliance.
2. Preference control. Give consumers frequency and topic choices instead of a single opt-out. Every complaint you convert into a preference change is a complaint that doesn't count against the ceiling.
3. Sunsetting and re-engagement. Suppress inactive subscribers after a defined period, with a win-back or reconfirmation send first. Yahoo recommends double opt-in at acquisition and periodic reconfirmation for inactive subscribers. Where you set that period depends on your buying cycle, which is why identifying and minimizing inactive subscribers (https://www.acoustic.com/resources/blog/5-steps-to-identify-and-minimize-inactive-email-subscribers) starts with defining what inactive means for your business.

Frequency is what ties these three together, and it's the hardest to see in standard reporting because the damage shows up weeks after the cause. Acoustic tracks a Fatigue Index that identifies where consumers are accumulating message fatigue, and reports messages per consumer by segment, so a cadence problem surfaces while it's still a cadence problem rather than a reputation one.

Work through your email deliverability checklist with Acoustic

Book an Acoustic demo (https://www.acoustic.com/demo) to see engagement reporting by recipient domain, preference management, and suppression running against your own sending data. You'll see which providers your mail is performing at and which segments are pulling your complaint rate toward the ceiling.

Email deliverability checklist FAQs

What should you do if emails land in spam at one provider only?

Treat it as a reputation problem at that provider rather than a content problem, since content that passed everywhere else didn't change. Check your complaint rate and authentication results for that domain specifically. Acoustic's reporting separates engagement by recipient domain, so the gap is visible before it spreads.

Do the sender requirements apply if you send fewer than 5,000 emails a day?

Yes. Google requires every sender to authenticate with SPF or DKIM, keep valid forward and reverse DNS, use TLS, and hold spam rates below 0.3%, and Yahoo sets a similar baseline for all senders. Crossing 5,000 a day adds DMARC, domain alignment, and one-click unsubscribe on top.

How is the 5,000-message threshold counted?

Google applies the 5,000-message threshold to messages sent to Gmail accounts in a day. Microsoft counts messages sent to its consumer email services from the same domain in the From address, and its published guidance states no time window, so the threshold follows your sending domain rather than your IPs.