Gmail deliverability: what to fix, in order

Gmail deliverability comes down to three things in priority order: authenticate properly, keep your user-reported spam rate under 0.30%, and generate enough genuine engagement that Gmail has a reason to trust your domain. Content tweaks matter far less than any of those. Here is how to work through them.

1. Meet the sender requirements exactly

Google's requirements for bulk senders are concrete, and failing them produces rejections rather than spam folder placement:

• SPF and DKIM both published and passing, with DMARC on the From domain. p=none is sufficient to satisfy the requirement.
• DMARC alignment — the visible From domain must align with the SPF domain or the DKIM d= domain.
• Valid forward-confirmed reverse DNS on the sending IP. The PTR must resolve to a hostname that resolves back to the same IP.
• One-click unsubscribe (List-Unsubscribe plus List-Unsubscribe-Post) on commercial bulk mail, honoured within two days.
• TLS on the connection for transmission.

These are the pass/fail gates. Check them with a message you actually sent, not a validator's theory, by opening *Show original* on a received copy and reading the Authentication-Results summary.

2. Respect 0.30%, aim for 0.10%

Google's stated threshold for user-reported spam is 0.30%, and its own guidance is to stay well below it. In practice, treat 0.10% as your ceiling and 0.30% as the point where damage is already underway. The rate is reported per domain in Postmaster Tools and it is computed from genuine "Report spam" clicks.

A single bad segment can take a whole domain over the line. If a spike appears, the useful question is which send caused it — not how to raise sending volume to dilute it. Dilution does not work; the rate is a ratio and Gmail reacts to the shape of the curve as well as the value.

3. Know what Postmaster Tools can still tell you

This changed, and a lot of advice still has it wrong. Postmaster Tools v1 was retired: senders were redirected to v2 from 30 September 2025 and v1 was gone by the end of 2025. The domain and IP reputation dashboards are permanently gone — there is no Bad/Low/Medium/High reputation grade to check any more.

What v2 does give you:

Set it up anyway — it is the only first-party view of how Gmail scores your traffic. But build your monitoring around spam rate and compliance, because the reputation grade people still ask about no longer exists.

4. Warm up before you scale, and keep the ramp boring

A new domain or a new mailbox has no history. Gmail's response to an unknown sender with sudden volume is to filter conservatively. Warm-up solves this by producing the only signals Gmail trusts for a stranger: messages that get opened, replied to, and rescued from spam by a human.

Replies are the strongest of those signals, which is why a warm-up that only opens mail is weak. Folder rescues — a message pulled out of Spam into the inbox — are the next strongest. Opens alone are noisy and, since Gmail's image proxy, partly synthetic anyway.

5. Use a subdomain for cold outreach

Send cold campaigns from a subdomain (go.yourdomain.com, mail.yourdomain.com) rather than your corporate root. The subdomain carries its own reputation, so a campaign that goes badly does not drag your invoices and password resets down with it. Warm the subdomain separately; it inherits very little from the parent.

6. Stop measuring placement by labels

This one costs people real money. Gmail's Promotions tab still carries the `INBOX` label. Any placement check built on the Gmail API's labels will count a Promotions-tab delivery as an inbox hit, so label-based numbers systematically overstate primary-tab delivery. If your dashboard says 98% inbox and your replies say otherwise, this is usually why. Use a check that distinguishes the tab, or treat your inbox figure as an upper bound.

What not to do

• Do not scrub "spam words" from your copy as a first move. Gmail is not matching a keyword list; a reputation problem does not care whether you wrote "free".
• Do not warm up by mailing your own team. Internal mail often bypasses filtering entirely, so it teaches Gmail nothing about how strangers treat you.
• Do not send to addresses you have not verified. Bounces to an unknown sender are weighted hard, and a dead list is the fastest route to a thin reputation.
• Do not add a plain-text unsubscribe line and call it one-click. The requirement is the List-Unsubscribe-Post header; a link in the footer does not satisfy it.
• Do not resume full volume after a pause. Two quiet weeks means a fresh ramp, not a hard restart.
• Do not look for a domain reputation grade. It is gone, and tools that still display one are inferring it, not reading it.

How MailPilot helps

MailPilot warms Gmail and Google Workspace mailboxes over OAuth — real sends, real replies, at a ramp you can see — and measures per-provider inbox placement with a seed-inbox network rather than inferring it from labels, so Promotions-tab delivery is reported as what it is. It also checks SPF, DKIM and DMARC alignment and tracks each mailbox's reputation daily, which is the part Postmaster Tools stopped showing.