Remote Server returned '< #4.4.0 smtp; 4.4.0 - Other network problem '[Errno 0] Error' (delivery attempts: 0)>'

[roldannicolas]

Hi Guys,

Has anybody encountered the same issue. I have one client which not receiving email from us and getting bounced. Interestingly not all emails are bouncing. I have this one mailbox which they are able to received emails and the rest were bouncing regardless if I'm using email domain which the same to the working mailbox.

I can always successfully telnet to their smtp test email however the status is

Queue mail for delivery

451 4.7.0 Timeout waiting for client input

Connection to host lost

I found this article but,the err code is different.

https://supportforums.cisco.com/discussion/11025191/440-other-network-problem-000-errno-60-operation-timed-out

Best regards,

[dmccabej]

Hello,

I looked through some past cases as well as the normal search channels, and this appears to be due to either something on the recipient end or your side manipulating the traffic. The first typical cause I would say is to check your firewall for any type of SMTP Inspection being performed on the traffic, as well as any other type of packet modification being done along the way within your network. 

Next, I would probably recommend reviewing the User Guide information below and setting up Domain Debug logs and a Packet Capture. This would provide you with further information on what is going on during the SMTP conversation for that recipient domain.

You can then upload that information here or possibly open up a support ticket and we can assist with troubleshooting.

ESA - Domain Debug Logging 

ESA - Setup/Start/Stop Packet Capture

Hope that helps! :)

Thanks!

-Dennis M.