Re: [Exim] HELO syntax checking in Exim 4

> [ On Thursday, March 14, 2002 at 15:09:36 (-0500), Dean Brooks wrote: ]
> > Subject: [Exim] HELO syntax checking in Exim 4
> >
> > Exim 4 appears to only allow me to turn off helo syntax checking
> > completely with the "helo_accept_junk_hosts" item. However, I really
> > don't want to do that either.
>
> You can't still have your cake and have eaten it too! If you're going
> to reject hosts with syntax errors in their HELO/EHLO greeting parameter
> then you have to reject those using underscores with equal prejudice to
> those who don't include a valid parent domain name. Both are equally
> bad and equally commonly misused.

With all respect, the discussion as to whether it is right or wrong
to accept items that violate RFC is purely academic.

The reality is that a large number of sites appear to use underscores
in the element portion of a domain in helo responses, and we can't run
a mail server in a vacuum - it has to operate in a real-world
environment.

The ultimate concern is that by rejecting underscores, we will be
rejecting valid mail. In 2 hours of running Exim4 in production
today, we blocked about 35 messages because of this. If we had
let it run, we would have most certainly generated customer service
calls within a day or two with people wanting to know why their
email was being rejected.

As it stands, my only options appear to be to either (a) disable
syntax checking completely, which isn't ideal or (b) hack
the source code, which I'm willing to do.

My original purpose in writing, though, is that if we're running into
this problem with 4.01, others will likely run into it too, so I
thought I'd find out if there was a way to change the pattern.

If there is no way to change the matching pattern, I'll just go
in and change the source, since RFCs be damned, it appears that many
sites in the real world are purely ignoring that part of the RFC.

Regards,

Dean Brooks
dean@???