[cobalt-users] [Raq4] host name lookups in sendmail - server appends default domain to unsuccessful lookups

[Chris Bell <chris@xxxxxxxxxxxxxxx>]

Hi,

I'm a bit rattled by sendmail and can't really get my head around it, so I 
was hoping someone can point me in the right direction.

I have a number of people running mailing lists on my server, which 
obviously have a number of invalid email addresses.

For instance, a lot of hotmail users either don't know or can't spell their 
email addresses, so you get mail being sent to addresses such as:

        user@xxxxxxxxxxxxxx
        user@xxxxxxxxxx
        user@hotmail

In some cases the email addresses were formerly valid but the domain they 
were attached to is no longer in operation or no longer has DNS entries due 
to large corporate collapse or similar circumstances, e.g.:

        user@xxxxxxxxxx

In both cases, when the MX lookup on the domain fails, the system seems to 
assume that it is in fact a host name, and my own domain gets appended to 
the end of it:

        ----- The following addresses had permanent fatal errors -----
        <ojay@xxxxxxxxxxxxxxxxxxxxxxxxxx>
        (reason: system config error)

        ----- Transcript of session follows -----
        553 5.3.5 one.net.au.blueskyhost.com. config error: mail loops 
back to me (MX problem?)
        554 5.3.5 <ojay@xxxxxxxxxxxxxxxxxxxxxxxxxx>... Local configuration 
error
        Reporting-MTA: dns; www.blueskyhost.com
        Received-From-MTA: DNS; syd-tds.austar.net.au
        Arrival-Date: Mon, 21 Jan 2002 17:06:02 +1100

and

        ----- The following addresses had permanent fatal errors -----
        kelcap13@xxxxxxxxxxxxxx
        (reason: system config error)

        ----- Transcript of session follows -----
        553 5.3.5 hotmail.com.au.blueskyhost.com. config error: mail loops 
back to me (MX problem?)
        554 5.3.5 kelcap13@xxxxxxxxxxxxxxxxx Local configuration error
        Reporting-MTA: dns; www.blueskyhost.com
        Arrival-Date: Mon, 21 Jan 2002 08:57:49 +1100

I would rather the bounce message say something along the lines of "MX 
lookup failed for [domain]".

Is this a sendmail or a DNS issue? Does sendmail use nslookup to do it's 
lookups? Should I be looking in the nslookup configuration, or in 
sendmail.cf (which I might add makes very little sense to me when I look at 
it!)?

Any advice or links to relevant info appreciated.

cb