Troubles with sendmail

[Andrea Venturoli]

Hello.

Not sure if this is the right place to ask (maybe ports@? Sendmail's 
support? Cyrus IMAP mailing lists?).

I'm experiencing a strange problem with an MX server (9.3 with 
sendmail+tls+sasl2+ldap-8.15.1_2) which uses the cyrusv2 mailer to store 
mail on another server (9.3 with cyrus-imapd23-2.3.18_10).

This is what I think is the relevant part of sendmail's MC config file:
> define(`CYRUS_MAILER_FLAGS',`A5 at w')
> define(`CYRUSV2_MAILER_FLAGS',`A5 at w')
> define(`confLOCAL_MAILER', `cyrusv2')
> define(`CYRUSV2_MAILER_ARGS',`TCP [mail.localdomain] lmtp')
> MAILER(`cyrusv2')



 From time to time some message is delayed and a warning bounce is 
generated with the following:

> Deferred: Name server: mail.localdomain.: host name lookup failure

Since this is utter nonsense (mail.localdomain is always resolvable), I 
investigated a bit and found out that what the above really means is 
that one of the recipient's domain (not *my* recipient) cannot be resolved.

An example might clarify:
_ a message is sent to user at mydomain.it and to user at otherdomain.it;
_ of course it arrives at my server (MX for mydomain.it);
_ but ir won't reach its mailbox (user at mydomain.it) since otherdomain.it 
does not resolve properly.



I understand I'm sort of asking for a shot in the dark, but believe me, 
I've been hitting my head on this for a long time and I cannot 
understand what the cause may be.
Of course I tried many searches on the web, but perhaps I cannot guess 
the correct terms to search for.
Any idea?

  bye & Thanks
	av.