It's your node.  Underscores in host names are not conformant with
RFC822, RFC1123, and the host name one.  I don't remember it's
number.  Some SMTP implementations enforce it, some do not.
 
Don't let your unix support people tell you that sendmail is a
reference implementation of the relevant standards, it is not.
Close but not.
 
--
Glenn A. Malling <[log in to unmask]>
Syracuse University Computing Services   +1 (315) 443-4111
220 Machinery Hall  Syracuse, New York 13244-1260
 
Postmaster for SUnix and LISTSERV.