Google is a popular search engine and email provider, headquartered in California. It offers both a freemail option (Gmail) and a range of online services for business domains (GSuite). They boast total automation and machine learning as their spam filtering and anti-abuse systems. There are few methods for contacting a human to review delivery issues, since options for human intervention in these kinds of processes are also limited. Instead all senders should be monitoring their domains at Google Postmaster Tools daily for insight into reputation and performance.
gmail.com, googlemail.com
18 responses across 7 reply codes
SMTP 421
4 responses
4.7.0
Gmail blocked this for low domain reputation. Check Postmaster Tools, fix authentication, and pause volume until reputation recovers.
4.7.0-2
Gmail blocked this because the content or links look suspicious. Clean the template, remove risky URLs, and retry at lower volume.
4.7.28
Gmail rate-limited your IP for unusual unsolicited traffic. Slow sends, scrub engagement, and review Postmaster Tools before ramping again.
4.7.32
Gmail deferred this because DMARC alignment is missing. Align SPF or DKIM with your From domain so DMARC passes, then resend.
SMTP 450
1 responses
SMTP 451
1 responses
SMTP 452
1 responses
SMTP 550
7 responses
5.1.1
Gmail says this mailbox does not exist. Treat it as a hard bounce and remove the address.
5.2.1
Gmail says this mailbox is disabled. Suppress it if it keeps failing.
5.2.1-2
Gmail permanently rate-limited this recipient. Confirm the address was not list-bombed, then suppress it if delivery never recovers.
5.7.1
Gmail permanently blocked this for low domain reputation. Check Postmaster Tools, fix authentication, and pause volume until reputation recovers.
5.7.1-2
Gmail permanently blocked this as unsolicited mail. Review consent, engagement, and complaint rates before sending again.
5.7.1-3
Gmail rejected this under the domain DMARC policy. Align SPF or DKIM with the From domain so DMARC passes, then resend.
5.7.1-4
Gmail rejected a missing or invalid From header. Fix the From name and address formatting, then resend.
SMTP 552
3 responses
5.2.2
This Gmail mailbox is permanently over quota. Retry later, but stop if the same address keeps bouncing.
5.2.3
The message exceeded Gmail's size limits. Reduce attachments and HTML size, then resend.
5.7.0
Gmail blocked an illegal attachment type. Remove risky attachments and resend a cleaner message.
SMTP 553
1 responses
Response catalog adapted from the MIT-licensed SMTP Field Manual by ActiveCampaign / Postmark.