The Email Deliverability Checklist: 22 Things to Fix, in Order

Most deliverability guides are an undifferentiated list where "set up DMARC" sits beside "avoid the word free". Those are not comparable in impact. This one is ordered — work top to bottom and stop when your placement recovers.

Tier 1 — authentication (do these first)

1. 1Publish an SPF record listing every service that sends as your domain. One record only; two is a misconfiguration that fails outright.
2. 2Check your SPF lookup count stays under 10. Exceeding it fails silently and permanently.
3. 3Enable DKIM for every sending service, using 2048-bit keys. In Google Workspace, remember to click *Start authentication* after publishing the record.
4. 4Publish a DMARC record, starting at p=none with a reporting address.
5. 5Read the DMARC reports for two to four weeks, fix any legitimate sender that fails, then move to p=quarantine and eventually p=reject.
6. 6Verify with a real message — send to Gmail, use *Show original*, confirm PASS on all three.

Since 2024 Google and Yahoo require this from bulk senders and weigh it for everyone. Full walkthrough in the SPF, DKIM and DMARC setup guide.

Tier 2 — list hygiene (the biggest ongoing lever)

1. 1Verify addresses before sending. Bounce rate above ~2% is a serious negative signal.
2. 2Never buy or scrape a list. The short-term volume is not worth the long-term reputation damage, and it is often unlawful.
3. 3Remove hard bounces immediately. Sending twice to a dead address is worse than sending once.
4. 4Suppress long-term non-openers. Someone who has ignored 20 messages is dragging down your engagement score for everyone else.
5. 5Honour unsubscribes within 24 hours, ideally instantly. This is a legal obligation as well as a reputation one.
6. 6Watch for spam traps. Recycled or pristine trap addresses in an old list are a fast route to a blocklist.

Tier 3 — sending behaviour

1. 1Warm up new domains and accounts. Start at 20–30 a day, increase ~30% weekly. There is no shortcut.
2. 2Keep volume steady. Spikes look like a compromised account.
3. 3Spread sends over hours, not minutes.
4. 4Stay inside provider limits — see Gmail sending limits.
5. 5Use a subdomain for bulk mail (mail.yourcompany.com) so a campaign problem does not poison your one-to-one correspondence.
6. 6Do not switch domains to escape a reputation problem. It resets you to unknown, which is worse, and it looks evasive.

Tier 4 — content and structure

1. 1Send plain-looking mail for one-to-one email. No template, no hero image, no styled buttons.
2. 2Keep the link count low. One is fine; five plus a tracked signature is a mailing.
3. 3Do not add bulk headers to individual email. A List-Unsubscribe on genuine one-to-one mail tells Gmail to file it as a campaign.
4. 4Watch the image-to-text ratio. Mostly-image messages read as advertisements.
5. 5Make sure a reply goes somewhere real. no-reply@ addresses suppress the single strongest positive signal available.

Tracking sits in this tier, and it is less costly than folklore suggests — a single first-party pixel is close to free, while rewritten links on a shared redirect domain carry real risk. The distinction is in does email tracking affect deliverability.

Tier 5 — monitoring

1. 1Set up Google Postmaster Tools if you send meaningful volume to Gmail. It is the closest thing to an authoritative scoreboard.
2. 2Keep seed accounts on Gmail, Outlook and a corporate domain, and check placement by hand on real sends.
3. 3Watch open rate by provider. A drop at one provider while others hold steady is your earliest filtering alarm — why open rates drop.
4. 4Track complaint rate. Above 0.1% is a problem; above 0.3% is an emergency.
5. 5Check blocklists if placement collapses suddenly.

If you are already in trouble

Stop sending campaigns. Continuing to send into a filtering problem deepens it. Then: verify authentication still passes, cut the list to your most engaged contacts only, resume at low volume, and rebuild from there. It takes weeks rather than days, and there is no version that is faster.

The diagnosis for how you got there is in why emails land in spam, and the Promotions-tab variant — less severe, still costly — in emails going to the Promotions tab.