G'day,
We are seeing this error across some servers/domains.
SMTP Error 451 4.7.500 Server busy. Please try again later.
This seems to relate to Microsoft determining a change in sending behaviour.
The error occurs when the recipient mail server's Exchange Online
Protection (EOP) service detects a significant change in the sending
mail server's previously established sending patterns.
Checking the sender.office.com system, it reports the most problematic
client machine as fine:
The IP address in question is not currently blocked in our system.
So, given it is causing a bit of havoc and vendors like cPanel have just
issued an article 4 days ago about it (so incidence rate is up), what's
the go?
https://support.cpanel.net/hc/en-us/articles/4408492985111-SMTP-Error-451-4-7-500-Server-busy-Please-try-again-later
If we can't resolve anything and it's deferring it many times (5+) then
what can we really do?
Hoping that some insights may be gleaned here! :-)
Many thanks,
Luke Thompson, CTO
The Network Crew P/L
E: luke.t@tnc.works
https://tnc.works
_______________________________________________
mailop mailing list
mailop@mailop.org
https://list.mailop.org/listinfo/mailop
