From: Niall O Broin (niall at domain magicgoeshere.com)
Date: Mon 24 Jul 2000 - 08:49:46 IST
For my sins, I'm setting up sendmail again for somebody. However, I've
encountered a slightly (is anything with sendmail ever slight ?) strange
problem. This site has a dial-up ISDN connection, so I have a smart host
defined. Whenever I try to have sendmail send queued messages, I get a
bounced mail with Returned mail: User unknown which is a bit depressing
because it's my address I'm using to test.
When I look at the bounced mail I see
----- Transcript of session follows -----
... while talking to relay02.cablecom.net.:
>>> RCPT To:<niall at domain magicgoeshere.com>
<<< 550 <niall at domain magicgoeshere.com>... Relaying denied
550 niall at domain magicgoeshere.com... User unknown
Now, I know exactly what's happening here i.e. relay02.cablecom.net will not
relay. However, this is not the smart host which I have defined, which is
mail.swissonline.ch. When I do an MX lookup on that I get this:
mail.swissonline.ch preference = 50, mail exchanger = mail.swissonline.ch
mail.swissonline.ch preference = 5, mail exchanger = relay01.cablecom.net
mail.swissonline.ch preference = 5, mail exchanger = relay02.cablecom.net
mail.swissonline.ch preference = 5, mail exchanger = relay03.cablecom.net
During various tests, I have had relaying denied from relay02 and relay03,
(it seems that relay01 is down). Now, what I'm presuming is happening
here is that sendmail is picking one of relay0? hosts for relaying, as the
preference of 5 tells it to. Unfortunately, these boxes don't relay.
mail.swissonline.ch DOES relay (tested by telnet) but unfortunately sendmail
doesn't choose to use it (of course). So, I have two questions.
1) Is my analysis correct (I'm pretty sure it is, but . . .) ?
2) How do I solve my problem ?
WRT 2), I have a couple of ideas.
i) Reconfigure sendmail to force use of mail.swissonline.ch - I don't
imagine this is possible, because it's plain wrong - it should use the
lowest preference relay available.
ii) Get the sendmail source and carry on as in i) and fsck the begrudgers -
probably :-) not a good idea.
iii) Run a local nameserver which is basically a cacheonly server, but has a
finagled preference for mail.swissonline.ch - I like this idea but I've an
idea I'll give Thomas Bridges apoplexy :-)
iv) Call the ISP and tell them to get their act together - don't hold out
much hope there.
This archive was generated by hypermail 2.1.6 : Thu 06 Feb 2003 - 13:06:57 GMT