Re: [exim] syntactically invalid argument(s) - rejected HELO

Marc Perkel wrote:

> I bet there isn't one in 1000 system admins that know that underscores
> aren't allowed in HELOs. That's not technical incompetents - it's just
> a stupid rule.

Underscore is not allowed only in HELO, it is not allowed in host names
at all.
Try to give your Windows 2000/XP machine name with underscore in it, and
you'll get
Microsoft warning that '_' is not allowed in DNS hostnames and may cause
problems for you.