Hello
i am somehow not an expert and just started a dedicated server (linux 7.3 with webmin). i have only one IP. i have registered 2 domains (www.domain1.com and www.domain2.com). i managed to setup correctly the virtual hosting in apache and use my hosting company's DNS (by the way they don't allow wildcard DNS for me, exemple xyz.domain1.com is not resolved ....).

i would like to setup my sendmail so that i can use email for my 2 virtual domains but as i said i don't have a DNS running on my server (i think i would need anyway a second IP to be accepted by registrant). I NEED HELP TO DO THIS, getting a sample sendmail.cf for this would be great. thanks!

you need to use sendmail's virtualusertable. It allows you to set something like:
user@domainA.com => userA
user@domainB.com => userB

Connect me offline if you want more help

Don't forget that you need to add your domains to /etc/mail/local-host-names or whatever file was specified to hold domains that will be receiving mail on the server.