Gmail unverified sender warning
Gmail displays “unverified sender” when a message lacks trustworthy authentication — typically missing or failing DMARC, or no aligned SPF/DKIM on the From domain. Bulk and marketing senders see this most often after Google’s 2024 authentication requirements.
Quick fix (3 steps)
- 1
Publish a DMARC TXT record at `_dmarc.yourdomain.com` with at least `v=DMARC1; p=none; rua=mailto:...` to begin monitoring.
- 2
Ensure SPF authorizes your sending path and DKIM signs with a d= domain that aligns with your From address.
- 3
For third-party ESPs (Mailchimp, HubSpot, etc.), enable authenticated sending / custom DKIM and verify CNAME records in your DNS host.
Common questions
Does p=none stop the unverified sender banner?+
Not by itself — you still need passing SPF or DKIM with alignment. p=none lets you monitor failures while fixing senders before moving to quarantine or reject.
Is this the same as 550 5.7.26?+
Related but different. Unverified sender is a mailbox warning; 550 5.7.26 is a hard SMTP rejection. Both stem from authentication gaps.
How do I fix this for Mailchimp or SendGrid?+
Enable domain authentication in the ESP dashboard, add their CNAME/TXT records to DNS, and confirm DKIM d= matches your From domain.