Murray-
Relay mail is designed to allow users (external to your local network) to
send mail through your servers. You can see how this can become a problem
if your servers are not properly configured or protected. If you disable
relay, but set the mail CLIENTS to "auth" outgoing mail, the sessions are
treated as though they ARE local and so the mail is sent. Anyone without a
username and PW is SOL. Anyone with a username and PW can send mail
perfectly.
If you don't lock down your server it *will* be discovered by spammers and
used to send spam. It's that simple. I didn't think it would happen to me,
as I only host a few domains, but within 2 weeks my servers were
spamming/DOSing another domain (sorry Ed@Marlin). The only real solution
I've found (aside from the wonderful 3rd party plug in products for IMail)
is to disable relay all together, and set the mail clients to auth for
outgoing mail. It's an easy option to set and can prevent numerous
disasters.
If you don't believe me, leave your relay open for a week or two and check
your logs daily. You should check your logs daily anyway, but pay close
attention to the file sizes of the logs- I ***GUARANTEE*** that if you
leave relay open, within 30 days the size of the log files will grow
exponentially as your IP/mail server name is spread among the spammers.
There are people out there whose time is dedicated exclusively to finding
mail servers that aren't protected. It's only a matter of time before your
server's ports are scanned and test mails are sent out by these people.
My advice (which solved the problem for me) is to disable all relay and set
the clients to auth for outgoing.
Joe Weirather
[EMAIL PROTECTED]
----- Original Message -----
From: "Murray Gray" <[EMAIL PROTECTED]>
To: <[EMAIL PROTECTED]>
Sent: Thursday, August 30, 2001 10:28 AM
Subject: [IMail Forum] Relaying mail
> Hi all,
>
> Please forgive the extra-newbie post...
>
> But i'm wondering whether someone can
> explain the implications of the 'Relay Mail'
> option.
>
> How useful is the feature, when would you
> use it - and how do you stop it being abused?
>
> Best regards,
>
> Murray.
>
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