[SOLVED] DKIM & Changing Server Hardware

[mrmarkuz (Markus Neuberger)]

Are there error details in /var/log/maillog or /var/log/messages ?

Let’s check the key with

opendkim-testkey

Here is another thread with same error, maybe related:

SMTP "451 4.7.1 Try again later" SMTP responses

@pagaille @stephdl In the end it was in fact two problems. The 4.7.1 was due to greylisting behaviour which you helped me with, thank you. This explains Scenario 2 in my first post. But also, one of my inbound MX IP was getting banned by fail2ban I found so I had to whitelist that IP which explained Scenario 1. Other MX IP we not banned, I am not sure why this was happening but everything is back to normal now.