When I send an e-mail from the device all is OK but I do not see anything on port 3101 in the DMZ ...??

When I send from the device an invitation to a meeting I have a red cross on the device and always nothing in the DMZ.

Which is the normal flow of an e-mail starting from the device?

In our DMZ we allowed the traffic in and outgoing on the port 3101 only for srp.eu.blackberry.net but this rule does not seem used for the ingoing e-mails ??? nothing in the log