Mail coming from your ISP for domain exampl1.com isn't rejected? Can it be that you fetchmail the mail? I ask because I bet you did not configure example1.com to be in class{w} (means treated to be local). Do so by adding that domain to /etc/mail/local-host-names. That is a plaintext flat file. Sendmail daemon restart is necessary.
echo '$=w' | /usr/lib/sendmail -bt ADDRESS TEST MODE (ruleset 3 NOT automatically invoked) Enter <ruleset> <address>
cluster1
[192.168.1.125] localhost.localdomain localhost example1.com
the example1.com is there.
The logs (/var/log/maillog) shows
Jul 18 15:38:00 cluster1 sendmail[6459]: k6IA80Op006455: to=< ank@example1.com>, ctladdr=ank@example1.com (512/513), delay=00:00:00, xdelay=00:00:00, mailer=local, pri=30776, dsn=2.0.0, stat=Sent
But the user ank is not able to receive the mails.
/etc/mail/local-host-names contains these entries
localhost localhost.localdomain example1.com
Second problem I am facing is that how do I configured sendmail to the
send the credentials of each user to the ISP account. For example if user1 wants to send the mail to the Internet the sendmail server should connect to ther ISP server with this user credentails (username and password ) and if user2 wants to send the mail to ther Internet then the sendmail should connect to the ISP server with the user2 credentails ( username and password).
http://www.sendmail.org/~ca/email/sm-812.html#812AUTH
It isn't possible to define multiple users for a single relay host target. (With Postfix you would require release 2.3)
For different relay selections based on the sender there is
http://anfi.homeunix.net/sendmail/smarttab.html
I will go through it.
Thanks & Regards
Ankush Grover