[IMail Forum] tracking blocked mail

[IMail]

We run multiple domains on Imail 4.07, generally without problems.  = However, we recently ran into someone who cannot send mail to any = mailbox in our primary domain.  That is, mail they send to mail (or my = co-workers) with disappear without even an error message.  It looks to = me like the mail is being blocked somewhere, but I can't find where. This customer uses Exchange 5.5, but they don't have any blocking set up = at their server.  They can successfully send mail to other domains that = we host on the same mail server, just not our domain.  So, for example, = their mail won't reach me at [EMAIL PROTECTED]. Does anyone have an idea how to trace the blocking for this?  They use = the Internet Mail Connector with their Exchange to retreive mail from an = ISP.  I wonder if the ISP is blocking the mail, but they're not very = cooperative in this investigation. Thanks, Ben Bednarz