Gmail delivery problems need a diagnosis before they need another campaign. Start with the message that failed: did Gmail reject it, defer it, accept it into spam, or place it in an inbox category the recipient did not expect?
This article was first published in 2018. We have revised the checklist to remove obsolete rules and separate published requirements from operational advice. For a maintained overview, see the current Gmail bulk-sender requirements.
1. Check which requirements apply
Google requires all senders to personal Gmail accounts to use SPF or DKIM, valid forward and reverse DNS, and TLS. Bulk senders also need SPF, DKIM, DMARC alignment, and one-click unsubscribe for marketing and subscribed messages. Google's sender guidelines own the complete requirements.
Google counts messages from the same primary domain together when determining bulk-sender status. Splitting a campaign across subdomains does not create separate thresholds. Check the sender FAQ, then check the Bird setup requirements for Gmail.
2. Establish what happened to the message
Keep the message ID, recipient, send time, sending domain and final SMTP response together. In the Email log, follow the recipient's events through acceptance, delivery, deferral or bounce. Acceptance by your sending service is a different event from acceptance by Gmail.
For a received message, inspect the received email headers. Compare a failed example with a successful one from the same message stream. A screenshot of the inbox alone cannot show which domain authenticated or which server accepted the message.
3. Secure the opt-in
Encourage your users to opt in to your communications instead of checking boxes by default. Record the signup source, the list the person joined, and the expectation you set about frequency.
For example: Katie opts in to JobSiteA's job alerts. That does not tell you she wants JobSiteB's newsletter, even if the two sites have the same owner. Design your subscription records around the choice Katie actually made.
Confirmed opt-in and double opt-in commonly describe the same flow: the subscriber follows a confirmation link after signup. They are not separate trust tiers requiring one versus two confirmation emails.
4. Read reputation data alongside your own results
Use Google Postmaster Tools to monitor Gmail reputation and spam reports. Google recommends keeping its reported spam rate below 0.1% and avoiding 0.3% or above. Those figures refer to Google's metric, not an interchangeable percentage from every email dashboard. Source: Google sender guidelines.
Record changes in authentication, audience, content and volume on the same timeline as delivery problems. That gives your team a concrete set of changes to investigate.
5. Treat opens as incomplete evidence
Google says it does not track open rates and cannot verify third-party open-rate measurements. A falling open rate alone does not establish spam placement. Source: Google sender guidelines.
Use recipient feedback, delivery events and business actions alongside engagement reports. Bird's tracking documentation explains how tracking works; check that configuration before comparing two campaigns.
6. Keep your subscriber list healthy
Remove invalid addresses from the sending path and respect opt-outs. Define an inactivity review around what the person subscribed to: a weekly newsletter and an annual renewal notice have different expected rhythms.
A fixed 30-day, 90-day or 12-month cutoff is not a universal Gmail rule. Write down your own retention and re-engagement policy, review its results, and do not use another campaign as a reason to restart mail to someone who opted out. Bird distinguishes deliverability suppressions from subscription preferences.
7. Make the sender and subject recognizable
Your business name and purpose should be clear as the sender. Test the From name, address, subject and reply destination together. A person should be able to recognize why the message arrived before opening it.
Use the same review for links. Read the anchor text and follow its destination: a button that promises an invoice should open that invoice, not a sales landing page.
8. Implement and test unsubscribe
Implement one-click unsubscribe using the current sending contract. Test the opt-out on an address you control, then verify that a subsequent marketing send respects it.
Test your own preference center too. If your application and email platform both maintain subscription state, identify which record controls the next campaign and how the other receives the change. A footer link that opens successfully is only the first half of that test.
9. Keep transactional and marketing purposes distinct
A password reset, an order receipt and a promotional offer serve different expectations. Label the message's category according to its purpose and keep your reporting separated by stream.
When troubleshooting, compare like with like. A healthy password-reset stream does not establish that an imported newsletter audience is healthy.
10. Verify authentication on a received message
Configure SPF, DKIM and DMARC in Bird, then send a message through the actual application path. Inspect the authentication results and the domain shown in the visible From address.
Repeat that check for each system sending on the domain. Your CRM, billing application and product backend may not use the same credentials or transport. Keep an inventory so a DNS correction for one sender does not silently exclude another.
11. Give each sending stream a clear owner
Different subdomains can identify different streams, such as newsletter.example.com and notifications.example.com. Document which application uses each one, which team maintains its DNS, and where failures are reported.
Do not rotate through domains to escape a delivery problem. Diagnose the affected audience and sending behavior before moving it to a different identity.
12. Inspect the full link chain
Check the original link, tracking redirect and final page. Use destinations that readers can understand. If an affiliate or another system adds a link, include it in your review rather than assuming your own HTML is the whole message.
This checklist does not treat every shortened URL or affiliate link as an automatic Gmail block. If a specific link is implicated, retain the affected message and the evidence for that conclusion.
13. Increase volume from observed results
Build your sending plan around the audience that expects the message, your established volume and the responses you receive. Review deferrals and bounces before increasing the next batch. Google's sending guidance recommends gradual increases and monitoring recipient feedback and server responses.
The previous version of this article included a daily schedule rising to millions of messages. We removed it because it could be mistaken for a Gmail-approved limit. Your plan should include a stop condition and a person who can act on it, not only a target volume.
14. Change one diagnosable part at a time
Before changing a domain, template, audience source or delivery provider, capture the current results. Send a controlled sample and compare the same recipient segment before expanding it.
Keep the old configuration in your incident notes. If several changes arrive together, you need enough evidence to distinguish an authentication failure from a change in the audience or message.
15. Separate inbox categories from spam
Ask the recipient where the message landed and inspect that example. A message in Promotions and a rejected message need different investigations. Avoid rewriting useful content merely to imitate a personal email or chase an assumed image-to-text formula.
End the investigation with a record someone else can use: the symptom, message IDs, provider responses, configuration change and result. For the broader diagnostic workflow, continue with Bird email deliverability.