There is such scheme:
The Internet (2 providers, bgp) - cisco 3845 - cisco ASA 5520 - an internal network
Thus at equipment interface are used vlan - i.e. ports on cisco work in a mode dot1q and virtual subinterfaces are created.
In an internal network the post server (freebsd 7, postfix) is established.
All scheme works as a whole normally, however occasionally on a mail server at sending of letters on external relays there are messages:
"lost connection with domain.ru [xxx.yyy.zzz.ttt] while receiving the initial server greeting"
And mail does not go.
There is a suspicion that a problem in cisco ASA 5520. Whether someone faced the similar? How to solve this problem?