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Error: 550 5.4.300 Message expired -> 451 Temporary local problem - please try later
Greetings, Since moving a specific domain to Office365 mails going out to a few domains always end up being returning with the above error 451 Temporary local problem. Then after a while the...
This looks like a case of graylisting… best work with the other side to add an exception for your domain or similar.
This looks like a case of graylisting… best work with the other side to add an exception for your domain or similar.
VasilMichev Thank you kindly for the reply, your suspicion was correct as the recipient mail server filtering had a static IP bound to the sender that was the old MX records, and hence it was permanently placing the sender in a grey-list.
Solved by requesting a removal.
regards,