I have Exchange 2003 SP2 servers in a Front End and Back End Configuration, The front end server delivers email externally using public DNS for lookups. The server is also an OWA endpoint and is published behind a VSAT link with 650ms latency and 1MB bandwidth.
Lately i notice that emails, especially to gmail.com, yahoo.com and my key partner domains take rather long to deliver (over 3 hours in some cases). This occurs usually in the late afternoons and has done so within the last 4 days.
My latency on the vsat link is around 700ms during such times. I am able to resolve external domains on the front end and am also able to open telnet sessions on port 25.
Incoming emails are however fast (within 60 secs) while this is occurring.
Any thoughts on what else to look at as a culprit in such a situation will be helpful.