Which does not tell me much. I'm thinking it's DNS related, and it's interesting that it's none of my custom ACL messages.
On Gmail's end, they are saying
Technical details of temporary failure:
Google tried to deliver your message, but it was rejected by the recipient domain. We recommend contacting the other email provider for further information about the cause of this error. The error that the other server returned was: 451 451 Temporary local problem - please try later (state 14).
Reverse DNS looks ok for Google.
18.104.22.168 resolves to "mail-ww0-f48.google.com"
Almost, if not all of my ACL defers have a custom message written to my log.
So I think this must be some low level Exim error.
Can anybody shed some light on how to track this down ?
p.s. Also getting this on some Google Apps domains.
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