Authentication

[Frank Louwers]

On Fri, Feb 18, 2005 at 10:52:33AM -0300, Roger Jochem wrote:
>    Some accounts in my server are used outside the company, via
>    notebooks. Because of some reason, all the messages send by these
>    users outside the company are marked as spam.

Probably because there are on a dialup dns blacklist...

>    The solution I used for that is to put these e-mail accounts in a spam
>    whitelist. But now, there are a lot of e-mails that forge e-mails, and
>    I receive lots of e-mails of possible "failed virus" with there
>    e-mails as senders, and these messages pass the server (becouse they
>    are in a whitelist).

We faced the same problem, and fixed it the following way:

- put smtp-auth on a different port than regular smtp (a lot of isp's
  filter tcp/25 anyway, so better use tcp/587). Make sure that the
  MTA setup on that port ONLY accepts smtp-auth, no regular smtp.

- put a filter/script/... in the MTA config that adds a specific header
  on mails received from that MTA-instance

- put custom spamassassin rules that gives a score -20 to mails that
  have that specific header.

Kind Regards,
Frank Louwers

--
Openminds bvba                www.openminds.be
Tweebruggenstraat 16  -  9000 Gent  -  Belgium

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