exim list subscriber wrote: >
> On the off chance that some folks may find this useful...
>
> The site here is making a move to have MUA clients use the MSA port,
> rather than using the regular SMTP port. To get a handle on laggards, we
> wanted to get some kind of ACL to detect a MUA when it connected. The
> way we've been deciding if a MUA is connecting, is by counting the
> number of Received: headers in the message. If there is only one, that
> being added by the server, then the message is from a MUA.
> ..[snip]... >
Don't try this in production, not unless that is you really want to
reject nearly every message sent from a Microsoft Exchange server.
It seems that Exchange does not add a 'Recieved' header for any message
that is submitted to it by standard Outlook clients. That really sucks,
as I tried this and it lasted for about 2 days. There were problems
with no Recieved headers being added by other MTA's as well, but
Exchange is by far the greatest offender.
>
> One of the interesting things, is that this MUA check is tagging a
> significant portion of spam, or rather, that spam which isn't forging
I thought the same thing... but...
> Received: lines. That's a different problem, but this is proving to be a
> good pre-screen by catching spam in the SMTP DATA phase.
>
