Sendail and DNS lookups
 

For the past few days I have been trying to set a mail server for our office. The problem is that sendmail starts very slowly and mail can only be sent from our server but can not be received. Telnetting on port 110 gives no errors. Also if I try to fetchmail for another account I get the "SMTP transaction error" message.
I checked with a dozen of forums and it appears that I'm having problem with my DNS(sendmail doing a reverse DNS lookup) but I can't quite figure out how to solve my problem.
I did what most people advise but the nothing changes.

Thanks in advance for any help!

And what happens if you try to telnet to Sendmail on port 25?

If there are reverse dns lookup problems, you will be able to read the offending mail addresses in the /var/log/maillog file.
If you logon to the server and do "dig -t MX " for a valid mail address domain, this will test the reverse lookup connection from the mail server.

eg dig -t MX yahoo.com will give you the ip number of the yahoo mail servers. (man dig for more options)
If that email is coming from a different source address, why would you want to receive it?

Regards,
Peter

A correct MX entry exists in the DNS setup. Telnetting port 25 is Ok too.
That's what really bothers me. Sendmail hangs are usually caused by the lack of or incorrect DNS setup but in my case those things are (or at least appear) to be fine.
For mail not being received - can aliases.db be the cause of teh problem.
And about fetchmail - I'm trying to fetch mail for people who have pop3 accounts on other servers but use machines here in our office.
I really need to fix those problems soon. Help the newbie, please.

Wouldn't it be better to start sendmail in something like verbose logging mode (sendmail -v -O loglevel=9), just to be sure it's DNS resolving and not something else? Same goes for fetchmail (and procmail if you use procmail filtering).

Also I think it would be a good thing to post the relevant parts of your configs.