Delays from Win Telnet to Linux RH Server

Hello - my first post! Have a Red Hat linux server running Courier mail. Trying to setup a 'mailbee' web server on windows 2008 server for read and write through browser. Got the setup and read part - but can't authenticate using the smtp. My outlook does that fine though. Used wireshark to find that the linux server replies to telnet port 25 using ports 49678, 49632, then 25. This causes long delay. Reading about a linux setting called rp_filter that changes the reply ports. But it doesn't do it to my linux clients, only windows. Haven't changed the setting on the linux mail server. Wonder if anyone has seen something like this before. Thanks in advance. Evannator!

 

Great suggestion. Thanks! I asked some consultants that used to work for us before posting here. Since your suggestion, I have posted on linuxforums.com - hope to get something good there!