Re: [exim] Underscore in domain names

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Author: John Burnham
Date:  
To: Renaud Allard, exim-users
Subject: Re: [exim] Underscore in domain names

> Is there an easy way (preferably without modifying source
> code) to configure exim to allow an underscore in a RCPT
> domain name? I don't mean only in EHLO, but really in the
> recipient domain name (address like <ddts@tmn_00.domain.tld>).
>

Yep. In fact how to do it is in the FAQ on www.exim.org in a slightly different
form. But to make life easy for you:

Q0732
Question

I would like to either warn or deny when a host uses an underscore in the EHLO
command.

Answer

First, set

helo_allow_chars = _

This tells Exim not to reject the EHLO or HELO command immediately. Once you
have done that, you can test for the underscore in an ACL. For example, to log a
warning for hosts in your LAN, and reject for other hosts, you could do
something like this:

deny  message = Underscores are not valid in host names
      hosts = ! +lan_hosts
      condition = ${if match{$sender_helo_name}{_}{yes}{no}}


warn  log_message = Accepted underscore from [$sender_host_address]
      condition = ${if match{$sender_helo_name}{_}{yes}{no}}



---
So, as you can see, it's the helo_allow_chars config you need to alter.
John