Sending Mail Issue

[John]

Hi Team,

We would like to report this issue in sending emails (outgoing). The user sent it last December 5, 2016 but the recipient received it on December 7, 2016. Based on my screenshot below the mail was queued on December 5 and it takes 2 day to delivered by December 7, 2016. We would like to know what is the common cause? and how to prevent?

[Libin Varghese]

Hi John,

The message tracking shows that the ESA completed processing the email without any errors and was unable to create a delivery connection (DCID) with the destination server.

The common causes for this would be the destination server is down, network connectivity, DNS lookup failing to determine the destination IP, TLS negotiation failed and was pending retry etc.

During such circumstances the ESA would re-attempt delivery as per the configured bounce profile which by default is up to 3 days.

You can monitor pending delivery emails from the GUI under Monitor -> Delivery Status and by using command "tophosts" from the command line.

As there are various reasons (external to the ESA) for not being able to create a delivery connection there would not be a common way to prevent it on the ESA.

A common troubleshooting method would be to attempt a telnet to the destination server over port 25 to comfirm connectivity, setting up domain debug logs and packet captures etc.

http://www.cisco.com/c/en/us/support/docs/security/email-security-appliance/117848-configure-esa-00.html

http://www.cisco.com/c/en/us/support/docs/security/email-security-appliance/118467-technote-esa-00.html

Regards,
Libin Varghese