Question : lots of 421 4.4.2 Connection dropped errors

Experts,

I have been having issues with my EBS 2008 installation which has been up and running for almost 1 year now.  We have experienced slow internet access and error messages relating to non-delivery of email and the two are definitely linked.  This can happen for 2 days in a row then disappear. It could happen twice a day and then not happen again for 2 weeks. Its very random and very annoying.  When the issue occurs, I can notice a high volume of traffic leaving the router (using the routers diagnostic tools).

I have since discovered that if i stop the transport service on the security server, internet access returns to normal. So I have now suspended all mail in the queue and if I let them go a few at a time they will be delivered without error. These emails generally have attachments ranging from 3 to 14 MB in size.

Any thoughts?

Answer : lots of 421 4.4.2 Connection dropped errors

Check your outgoing queue.
Check the logs on the exchange to determine whether the spike in bandwidth use is because of a large amount of incoming,outgoing email, or a combination of the two.  You might be getting a massive influx of SPAM email that your router/exchange is rejecting, but the connection and some data is being transmitted using up the bandwidth. i.e. there are 10 connection per minute submitting a spam/virus laden email of 50k that is processed and rejected by the anti-virus/anti-spam process on the secure gateway.  Even though the message never makes it to the exchange server, 500K/minute of bandwidth are being used up.