Cisco ESA unable to process incoming mail from Microsoft Office365

[sengjiunn]

Hi,

I am doing a ESA POV for my customer. Deployed the ESA sitting on internal network with one-arm deployment. Firewall is doing the NAT to route incoming SMTP traffic to ESA and then their exchange server.

We are facing issue with Microsoft Office365. Where sender that using Office365 unable to send email to internal users. From the ESA mail logs, there is always queued for delivery message although customer has configured receiving connector on their exchange server with anonymous settings.

Looking to hear from you urgently.

Thanks & Regards,

Steven

[Libin Varghese]

Hi Steven,

Emails queued for delivery would suggest the Ironport is not able to communicate with the destination server over port 25. This could be due to a variety of reasons such as TLS, DNS or other network issues.

Ideally the command "hoststatus domain.com" would show you the error faced on delivering to the domain and you can also confirm connectivity using a basic telnet command to the destination server IP.

telnet xxx.xxx.xxx.xxx 25

For urgent requests I would recommend opening a TAC case by calling one of the below numbers.

The CIN contact numbers are:

North America   +1 800 553 2447
Asia-Pacific       + 612 8446 7411
Australia            + 1 800 805 227
Europe               + 32 2 704 5555
UK                      + 0800 404 7778

Thank You

Libin

[sengjiunn]

Hi Libin,

Thanks for your reply. Attached the result after i executed the "hoststatus domain.com".

The connectivity has no issue with telnet at port 25 also.

Thanks

[Libin Varghese · Accepted solution]

The email is being bounced upon creating a delivery connection with the exchange IP 192.168.10.3 with the error 550 5.1.1 User Unknown

This would be a configuration issue on the exchange side as explained in the below article.

https://support.microsoft.com/en-us/kb/2773786

I do not see this as an issue on the ESA itself.

Thanks

Libin