SendMail sending garbage mails

[Duncan]

> Hi friends,
>
> I have some problems with my sendmail server.
> it has sending some garbage mails to outside and that
> mails bouncing back to on different user that is not
> existing users.
> the error are like
> ----- The following addresses had permanent fatal
> errors -----
> vbqdfwhgvokn at centrum.cz
>     (reason: 550 5.5.1 No such user here)
>
>    ----- Transcript of session follows -----
> ... while talking to data2.centrum.cz.:
>
> >>>>>> DATA
>
> <<< 550 5.5.1 No such user here
> 550 5.1.1 vbqdfwhgvokn at centrum.cz... User unknown
> <<< 503 5.5.2 Waiting for RCPT command
>
> Subject:
> Returned mail: see transcript for details
> From:
> Mail Delivery Subsystem <MAILER-DAEMON>
> Date:
> Thu, 15 Jul 2004 21:14:34 +0530
> To:
> vbqdfwhgvokn at centrum.cz
>
> The original message was received at Thu, 15 Jul 2004
> 21:14:34 +0530
> from root at localhost
>
>    ----- The following addresses had permanent fatal
> errors -----
> craig at abc.net
>     (reason: 550 5.1.1 User unknown)
>    ----- Transcript of session follows -----
> 550 5.1.1 craig at abc.net... User unknown
>
> could any one please tell me how to stop this.
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> https://www.redhat.com/mailman/listinfo/redhat-list

Well you definately need a firewall on your loopback interface which does
not allow outside packets to connect  except  yo ISP to smtp port
etc..Basically do not allow packets from the outside .Else u have a machibe
in your LAN with a virus that is spamming , u iwll have to monitor your
maillog .
Wat do others think ????
Rgds

Duncan Rack