Sorry, you lost me there. Try adding some "." to separate sentences.
Check if I got you right:
you have 2 mail servers (I suppose you're referring to MTAs like sendmail, postfix, etc). On one of the machines, you have a bunch of users that can't login (something like disabled accounts).
Then you say that you can send out mail (I suppose via /bin/mail), but the others can't.
But I don't really understand what "connection to server2" has to do with it. Do you mean that the others try
to send out mail from one machine and the mail is then routed to a mail server (MTA) on the second one?
If so, did you remember to open the SMTP port on server2's firewall?
Try (on server1):
This will try to connect to server2 on the SMTP port (25). If it succeeds, then you can send mails to the sendmail/postfix/... on server2. If it fails, most likely causes would be an intervening firewall or
the fact that server2's MTA isn't configured to listen to port 25 on it's external network interface (ie maybe just listening to it's "localhost" loopback interface, which is unreachable from server1).