Deliverability begins before the subject line. Mailbox providers evaluate whether the sending domain is authenticated, whether recipients expect the message, how they respond, and whether leaving the list is easy.
Google's requirements are a useful operating baseline even when a campaign is below the bulk-sender threshold. This checklist translates the technical requirements into decisions a campaign owner can verify before scheduling.
Know which requirements apply
Google requires all senders to Gmail accounts to use SPF or DKIM authentication, valid DNS, TLS, valid message formatting, and a spam rate below 0.3 percent. Google recommends remaining below 0.1 percent and avoiding 0.3 percent or higher.
A sender delivering more than roughly 5,000 messages to personal Gmail accounts in a day must meet additional requirements, including SPF and DKIM, DMARC, From-domain alignment, and one-click unsubscribe for marketing and subscribed messages. Treat the threshold as a classification, not a target to work around.
Authenticate the visible sending domain
SPF identifies servers allowed to send for a MAIL FROM domain. DKIM adds a cryptographic signature associated with a domain. DMARC checks whether the domain visible in the From address aligns with the domain authenticated by SPF or DKIM and defines a policy for failures.
Mailbox providers recommend authenticating email for reliable delivery. In a managed sending workflow, the customer should verify a domain and choose a sender address from that domain rather than borrowing a platform-owned identity.
- Publish the required DKIM DNS records.
- Configure a custom MAIL FROM domain when appropriate.
- Publish a DMARC record and monitor reports.
- Use a From address that aligns with authenticated domains.
- Test the received message headers before a live campaign.
Make unsubscribing easier than reporting spam
Marketing messages should include a clear unsubscribe link in the email body. Bulk senders to Gmail must also support one-click unsubscribe through the List-Unsubscribe and List-Unsubscribe-Post headers.
The visible link and one-click header serve related but different purposes. Include both where required. Process the request promptly and suppress the address from future eligible campaigns.
List-Unsubscribe: <https://example.com/unsubscribe/token>
List-Unsubscribe-Post: List-Unsubscribe=One-ClickProtect reputation with audience discipline
Authentication proves who sent the email; it does not prove that the recipient wanted it. Send to people who expect the message, confirm addresses when they subscribe, remove invalid recipients, and respect prior opt-outs.
Monitor hard bounces, complaints, and Gmail Postmaster Tools. Suppression should happen before the next campaign, not after another delivery attempt. Mailbox providers expose different complaint signals, so direct reputation monitoring remains important.
Increase volume gradually
A newly verified domain does not immediately have a stable sending reputation. Google advises increasing sending volume slowly, sending at a consistent rate, and avoiding sudden spikes. The larger the intended volume, the more gradual the ramp should be.
Campaign software should enforce warm-up and account-level limits. A marketer should see a clear scheduling blocker rather than learning about a reputation problem after the campaign launches.
Pre-send deliverability checklist
This article is operational guidance, not legal advice. Requirements can change, and organizations should review the current mailbox-provider rules and laws that apply to their recipients.
- Verify the sending domain and approved From address.
- Confirm SPF, DKIM, DMARC, alignment, DNS, and TLS readiness.
- Confirm audience permission and campaign relevance.
- Remove invalid, unsubscribed, bounced, and complained addresses.
- Include visible and one-click unsubscribe where required.
- Review the subject, From name, body, links, and postal information.
- Check planned volume against warm-up and account limits.
- Monitor delivery, bounce, complaint, and Postmaster signals after launch.