On (2003/11/12 11:17), Tim Jackson wrote:
> > How do you allow underscores in the HELO check ?
>
> helo_accept_junk_hosts or helo_allow_chars
>
> But please don't use them indiscriminately, because not only will you get
> more junk, you'll encourage the people with misconfigured MTAs to believe
> that they're in the right.
>
> Much better to tell them to go change their DNS hostname to something
> sensible. If they're an Exchange-using idiot, then they will probably moan
> that changing their NetBIOS name will break everything else - however, my
> (non-authoritative) understanding is that it is possible to change the
> Internet hostname independently of the NetBIOS name on Windoze.
As usual, Exim allows you to have your cake and eat it too. :-)
I have this in my Exim configure file:
# In main:
acl_smtp_helo = check_helo
helo_allow_chars = _
# In acls:
check_helo:
#
# Deny illegal helo arguments from hosts whose operators haven't
# contacted us and asked us to work around their problematic
#configurations.
#
deny message = syntactically invalid argument(s): $sender_helo_name
condition = \
${if \
and { \
{ match {$sender_helo_name}{_} } \
{ \
!eq \
{${lookup{${lc:$sender_helo_name}} \
lsearch{/usr/local/etc/exim/broken_helo_hosts} \
{yes}{no} \
}} \
{yes} \
} \
} \
{true} \
}
#
accept
This means that folks with broken MTAs will, by default, get rejected.
Often, these folks are customers or vendors. When they make contact,
I explain the problem. Usually, renaming an Exchange server requires
more work than they can manage, so I add their broken HELO name to the
broken_helo_hosts file until they can fix the problem.
So you have education taking place, but not at an indefinite cost to
business.
Ciao,
Sheldon.
