>Is there a reason why addresses with an underscore in the domain name would
>suddenly begin bouncing?  We just reinstalled 1.8c (we were using an early
>build of 1.8d, but our server melted down and had to be replaced ...).
>
>Sherry Beauchamp

The real question is why it would have accepted it previously.  Underscores
aren't generally allowed in domain names.  I did a search in the LSTOWN-L
archives and found the following in a message from one Melvin Klassen:

>According to Internet RFC 1912 ("Common DNS Operational and Configuration
>Errors", February 1996, D. Barr, The Pennsylvania State University):
>
>   Allowable characters in a label for a host name are only ASCII letters,
>   digits, and the "minus" character.  ....
>   The presence of underscores in  a label is allowed in [RFC 1033],
>   except [RFC1033] is informational only, and was not defining a
>standard. ...
>   Note that the rules for Internet host names also apply to hosts and
>   addresses used in SMTP (See RFC 821).

A few years back Eric Thomas said that LISTSERV itself wouldn't have a
problem with domain names with underscores in them but most SMTP servers
would, but of course I don't know whether this is still correct.

-jwgh