Author: Dean Brooks Date: To: exim-users Subject: Re: [Exim] HELO syntax checking in Exim 4
> > 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.
>
> Ultimately by rejecting any connections with any kind of syntax error in
> the HELO/EHLO parameter will result in rejecting valid e-mail.
>
> Make up your mind -- do you want to risk it or not? Do you want to
> enforce the requirements placed on the client-SMTP by the RFCs or not?
I have no problem with Exim staying true to the RFC. That's what helps
keep standards from leaking. My original question was whether there
was a way to change HELO pattern matching - not whether it was right
or wrong for our organization to deviate from RFC.
The main thing that list members should be aware of is that the
pattern matching of Exim's HELO syntax checking *changed* between Exim 3
and Exim 4. Exim 3 permitted underscores, whereas Exim 4 does not.
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.
