Using the SMTP component of IIS v5 to relay mails in / out of an Exchange 5.5 server.

W2000 SP3 with GFI Mail Essentials installed. I don't think it's a Mail Essentials issue though.

Outbound mails hit the IIS queue and you can see the SMTP try to send out the mail through the logs ie

EHLO
MAIL
RCPT
DATA (or BDAT)

but it never ends the message and issues the QUIT command.

What's strange is messages to some mail servers go out fine, others just get stuck and keep getting retried.

Any thoughts?

TIA,

Chris.