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

Igor Robul wrote:

> Marc Perkel wrote:
>
> 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.
>
Yes - but - Exim does allow the HELO to not be a DNS name at all and it
allows that there might not be a HELO at all. So I think it's is at
least inconsistent with other loose rules regarding HELO.

Quite frankly - I'm not sure that the HELO has any useful functionality
in the first place and I wonder why it even exists.