What 553 5.1.2 means
The message Gmail attaches to this code is “We weren't able to find the recipient domain.”, as written on its reference page. The first digit says how final it is: a 5xx reply is permanent for that message, so the sending server gives up and returns a bounce. The enhanced status 5.1.2 says what class of problem it is: dns. A DNS record is missing on one side: no PTR for the sending IP, or no MX or A record for a domain.
Why it happens
A record the receiver expects is missing. That is usually no reverse DNS on the sending IP, or a domain with no MX or A record, which makes the sender look like it cannot receive replies. Receivers treat that as a sign of throwaway infrastructure.
What to do first: The recipient domain has no MX or A record: a typo or a dead domain. Remove the address.
Why warming does not fix this
Warming builds sender reputation. 553 5.1.2 in this form is a dns problem, and no amount of engagement history changes it. Fix the cause and the bounce stops; warming is for what comes after, when the mail is accepted and the question becomes which folder it lands in. See how warming works for that part.
How to fix it, in order
- Publish the missing record (PTR for a sending IP, MX or A for a domain)
- Re-test after propagation with the auth checker
Related codes
- 550 5.7.25 (Gmail): sending IP has no PTR record
- 421 4.7.0 (Gmail): very low sending IP reputation
- 550 5.7.1 (Gmail): policy prohibits the email
- 550 5.7.1 (Gmail): IP not authorized to send directly
- 550 5.7.1 (Gmail): very low sending domain reputation
More on Gmail
- Google Workspace emails going to spam: the Postmaster-led diagnosis, dashboard by dashboard
- Gmail and Yahoo bulk sender requirements: the rules behind Google's authentication and spam-rate rejections
- Google Postmaster Tools domain reputation: what the reputation tiers and the spam rate mean
Questions about 553 5.1.2
What does 553 5.1.2 mean?
Gmail returns 553 5.1.2 with the message "We weren't able to find the recipient domain.": recipient domain not found. A DNS record is missing on one side: no PTR for the sending IP, or no MX or A record for a domain.
Is 553 5.1.2 a hard bounce or a soft bounce?
A hard bounce for that message: the 553 reply is permanent, and the message is not retried. Whether the address should be removed depends on the cause: here the fix is on the sending side, not the list.
How do I fix 553 5.1.2?
The recipient domain has no MX or A record: a typo or a dead domain. Remove the address. Gmail's own reference for the code is linked on this page.
Does email warmup fix 553 5.1.2?
No. 553 5.1.2 in this form is a dns problem, and warming builds reputation, which is not what is failing here. Fix the cause and the bounce stops.