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Re: [suse-security] Mailing Trouble ?!

Thanks for the replies.
I posted it to SuSE-security because it´s the only SuSE forum I subscribe
to, also I believed that my problem might be the result of either an
over-eager anti-spam software or my firewall.

> Your mx records show
> 0 router.leat.ruhr-uni-bochum.de
> 20 mi.ruhr-uni-bochum.de
> router.leat.ruhr-uni-bochum.de points to two A records and
>, both of which accept connections on port 25, but just
> no error message or anything. is my external NIC, my internal NIC.
Communication from outside my domain to is blocked by the
firewall, this is intended.

Where can I change that so that my servers gives back the appropiate message
? I looked
at sendmail.cf but didn´t find anything I deemed useful in that matter.
Also, my knowledge of sendmail
is pretty limited.

> mi.ruhr-uni-bochum.de points to two A records and
>, both of which accept connections on port 25 and give back a
> 220 message.
> I am guessing that because router.leat.ruhr-uni-bochum.de is accepting
> connections, but giving out a 220 message or any message for that matter,
> they may well be correct in not going to the backup mx.

So, how come I sometimes have mail communications from and to that specific
site, and sometimes don´t ? Also, this mail server has been running
continuously for two years now, and I never missed any mail that I know of.

> One other quick question, what does this problem have to do with Suse
> Security???

See above :)

Thanks for the help,


> ----- Original Message ----- 
> From: "remote" <remote@xxxxxxxxxxxxxxxxxxxxxxx>
> To: "SuSE-Security-Liste" <suse-security@xxxxxxxx>
> Sent: Tuesday, September 07, 2004 10:07 AM
> Subject: [suse-security] Mailing Trouble ?!
> Hi !
> I run a mail server at a university institute. Recently I noticed that
> from and to a certain site disappeared without notification. After mailing
> to the sysadmin of that site he told me that his mail server software had
> given up sending mail to my server after having received an error code 421
> whichhe says means that the server is temporarily unable to accept SMTP
> connections. His system seems to be either unwilling or unable to switch
> the alternate mail server in my MX records.
> My problem is, I don´t know if there is anything wrong with my system. As
> far as I know, this is the only case where my domain had trouble receiving
> or sending mail. We experience sluggish mail traffic at times here, but
> according to my university´s computing center that is their problem
> their server are running near full capacity.
> As far as I have been able to find out, my DNS service is configured
> correctly (Name resolution and reverse resolution work, my MX records are
> correct and can be accessed from outside) and my domain is not listed on a
> blacklist.
> My questions :
> 1) Is the inability to establish mail communication to and from this
> specific site my problem or theirs ?
> 2) How can I check if my system yields this error-code 421 message ? If
> what can I do to correct it ?
> .
> My server is a Linux box running SuSE 8.0, sendmail version is 8.12.2.
> Thanks for the help,
> Jörg

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