On Fri, 15 Mar 2002, Greg A. Woods wrote:
> > My concern is that many sites may set accept_helo_junk_hosts to deal
> > with this, which actually makes a worse deviation from RFC than simply
> > permitting the underscore itself.
>
> The point is that if you're going to allow underscores then you may as
> well allow all the other things that are commonly used but which cannot
> possibly be valid hostnames (and which are not literal IP addresses :-).
>
> You (and we) only gain something if you enforce the actual rules, not
> some abberations of your own invention.
That is precisely why I made the change in Exim 4. Exim 3 treated
underscore as a "special aberration" (there was an option to enforce
it), and I decided that allowing only one kind of syntax error was
silly and inconsistent. Note that this IS documented in doc/Exim4.upgrade:
. helo_strict_syntax has been abolished. The default is now to enforce strict
domain syntax for HELO/EHLO arguments. You can use helo_accept_junk_hosts if
you want to avoid this.
The checking is done by simple code, not by regexp. If you want to patch
it, look at line 552 in smtp_in.c.
I suppose I could make things easier by inventing an option which lists
the characters you are prepared to accept, other than alphanumerics.
--
Philip Hazel University of Cambridge Computing Service,
ph10@??? Cambridge, England. Phone: +44 1223 334714.
