[Exim] Error from Exchange server

There's a server that's having trouble sending email to both of my exim
machines; this is the error being logged:

2003-02-07 15:15:25 rejected EHLO from [64.221.212.2]: syntactically
invalid argument(s): twinsoft_bdc.twinsoft
2003-02-07 15:15:25 rejected HELO from [64.221.212.2]: syntactically
invalid argument(s): twinsoft_bdc.twinsoft

Looking at that, I'd say the problem is that underscores are illegal in
domain names, but I wanted to run it by the experts before I insist to
the Exchange admin that it's his problem.

Thanks!

--
Mark Edwards
Engineer
Mr. Toad's
San Francisco, CA