I am running exchange 5.5 with sp4 on nt4 with sp6. Emails are routed through MS ISA. The problem I am having is that one of the company we work with, they can't seem to send us any emails. What ever they send it get's bounced back. I know they can connect to us but my server drops their connection. They can also telnet through port 25 and they get dropped also. I have looked at the logs and there don't seem to be anything unusual.