Re: [SLE] Postfix question
From: Theo v. Werkhoven (twe-suse.e_at_ferrets4me.xs4all.nl)
Date: 09/20/04
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Date: Mon, 20 Sep 2004 19:24:36 +0200 To: suse-linux-e@suse.com
Mon, 20 Sep 2004, by usr@sanctum.com:
> On Sunday 19 September 2004 02:49, Jeffrey L. Taylor wrote:
> >Quoting Bob S <usr@sanctum.com>:
> >> Hello SuSE people,
> >>
> >> Have a question about Postfix. Back about the 9th or 10th I upgraded
> >> KDE to 3.3. That included Kmail which is my only e-mail program.
> >
> >You need to have some kind of Mail Transfer Agent (MTA) like Postfix
> >on most Linux systems. It looks like it is not correctly setup,
> >though there are other possibilities like your ISP is blocking outgoing
> >mail that bypasses their SMTP servers, a common attempt at reducing
> >SPAM, especially from zombies/trojans. Linux.local may be your
> >machine, check the IP address.
> >
>
> Thanks to all who contributed to this question. Simple question generated
> quite a large response and as a result I learned quite a bit. Do have a few
> specific questions from the various responses.
>
> Jeffrey, Sent off an email to my ISP tonight asking about the blocking and/or
> the POP before SMTP thing. Will let the list know their response.
>
> Theo, you stated:
> >That's not the problem, the problem was a DNS lookup failure
> >according to the bounce message, Postfix couldn't find a place to
> >drop the mail because the DNS didn't give it one, and so it returned
> >the mail to sender.
> Please elaborate. Where and why couldn't Postfix find the DNS. The DNS for my
> ISP ? or for the recipient? And if so how do I check it? The DNS for my ISP
> is defined in PPP someplace.
It wasn't that Postfix couldn't find a DNS, but the DNS didn't
answer the query that the DNS received from Postfix, and so POstfix
didn't know where to drop off the mail.
That's the way mail servers work: a user wants to send a mail to
user@example.com. Postfix gets the mail from the Mail User Agent
(the mail client program like e.g. kmail), looks at the recipient
address (example.com) and tries to find out which mail host is
responsible for the example.com domain.
Postfix does this by first asking root DNS servers for what DNS knows
anything about the .com top level domain, then it asks the first
responding server what DNS knows about example.com domain, and if
Postfix got that address it asks example.com what host receives the
mail for example.com.
If Postfix finally knows the answer (e.g. mail.example.com) then it
can send the mail on to its destination.
If one of the DNS server doesn't answer (usually the one responsible
for the domain), the request from Postfix times out and the mail
never gets send.
In your case the DNS responsible for .com tld didn't know
esupport.com, so the query ended there.
You can check with 'dig -t mx example.com' if your 'resolver' can
find the Mail eXchange record for example.com.
> Now, if I read the posts from Theo, I do not NEED an MTA - OK - understood ??
Not one running as daemon, if all you do is Desktop stuff, no.
> But I DO have Postfix. According to Patrick Postfix is needed internally by
> SuSE for things like mail for root etc. Good- OK Carlos says that Kmail
> actually uses Postfix to send it's mail. ( required?) And Patrick agrees,
> stating: >"Yes, he is mixing daemon with MTA. The MTA is still
> required/installed." ----- Or, only if it is there to use? But Kmail can
> actually do it all by itself? A little confused here !!
Kmail has it's own SMTP engine, and doesn't need an external mail
server like e.g. Mutt.
You can set your ISP's mail gateway address in kmail and drop the
mail directly into their care.
For system messages you wish to receive you do need a MTA though.
Theo
-- Theo v. Werkhoven Registered Linux user# 99872 http://counter.li.org ICBM 52 13 27N , 4 29 45E. + ICQ: 277217131 SUSE 9.1 + Jabber: gurp@nedlinux.nl Kernel 2.6.5 + MSN: twe-msn@ferrets4me.xs4all.nl See headers for PGP/GPG info. +
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