In the past month we have suddenly become unable to receive inbound smtp traffic from a specific client.
After some packet capture footwork it appears that whenever the external mail server tries to access our internal mail server via smtp our PIX treats the connection as a VPN session as is noted by the ISAKMP transaction that is initiated.
It turns out that the external mail server is on the same network as a Lan-2-Lan that we have set up @ a colo. I'm under the impression that perhaps our Lan-2-Lan setup between our 515E and the ASA5510 on the colo end is misconfigured and instead of simply passing smtp traffic to the server, tries to initiate a VPN session.
I'd be happy to provide further details but wanted to put the basics out there to see if anyone had some suggestions I could follow up on.
I'm currently unable to disable the lan-2-lan due to service disruption at this time but think that this would quickly confirm whether the lan-2-lan is the actual culprit.
Thanks in advance for any input.