5.3.4 message size exceeds limit

[mohammadrezafathikohi]

Hello,

when i send an email from outside to my cisco esa which is connected to my exchange 2019 server, I see lots of logs showing that message header exeecds limit. And the incoming email will drop eventually. What should i do to solve the issue?

[Libin Varghese]

Please refer to the below article for steps to increase the allowed header size limit.

https://www.cisco.com/c/en/us/support/docs/security/email-security-appliance/118495-technote-esa-00.html

Ideally, once you've narrowed down the problem causing header work with the sender to correct it.

Keeping an unlimited header allowed size would not be recommended as a permanent change.

Regards,

Libin

[mohammadrezafathikohi]

I replaced the internal domain name with the actual public domain name of our company in the SMTP route setting and Emails started to flow in. Thank you for your time.