I have posted this several times using various descriptions of the problem. !!!I REALLY NEED EXPERT HELP HERE!!!! I have researched this situation everywhere and still nothing works. I put my exchange server inside the firewall and used a IIS5 (windows 2000) SMTP server to FORWARD MAIL to it. Only remote domains in the list that I entered are forwarded. I specified the exchange server IP in 's for each remote forwarded domain. ALL email is forwarded now. I have not installed virus or Spam filtration software on the forwarder. All seemed fine, until I realized that all INBOUND emails with a "return-path: <>" in the header are being dropped in BADMAIL. I look on the event log of the forwarder, and see: ===================================== Event Type: Warning Event Source: smtpsvc Event Category: None Event ID: 4000 Date: 1/28/2003 Time: 6:16:54 PM User: N/A Computer: MAILGUARD Description: Message delivery to the remote domain 'conway.com' failed for the following reason: Unable to successfully connect to the remote server. Data: 0000: 3a 02 04 c0 :..À ===================================== This happens once for every message with a "return-path: <>" in the header Further research revealed that these messages are NDRs from AOL but MOSTLY messages from List servers. We NEED to get these emails!!! So, here's what testing I have done.. If I drop these messages into the PICKUP folder, they get delivered. I telnetted into the local host for the forwarder, sent a message from <> to myself. It arrived. I telnetted into the exchange server, sent a message from <> to myself. It arrived. (I am assuming these emails are the same as the ones that have a "return-path: <>" in them.) I send a message to the foreign list server with a command that makes it reply, and it too lands in BADMAIL. If email arrives from an exterior server with "return-path: <>" in the header, it drops to badmail and I cant stop it. What should I do? Im completely stumped, and this has been going on for over a month now.