Sendmail configuration on Linux

Some of the domains on my server aren't able to receive email and others are unable to send email. I need someone to go through the sendmail configuration files and fix that problem, plus check for any other problems there might be with other accounts on the server (15 domains/accounts max). Further info: We're running cPanel on the server. The reason for the problem in the first place is that we had a hard drive problem and had to transfer over accounts manually from a secondary hard drive.