How to configure email.Any Tips?

Hi,
I have been pretty slack on this subject & have to admit I just neglected my email accounts after trying to configure them.
This is because I can’t get them to work.
By this I mean I have st up email accounts in my sites control panel,I followed the instructions from Laughing Squid to the letter.And yet I can not send or receive emails at all from the accounts.
I have tried setting up the accounts with Mozilla Thunderbird & webmail but no joy.
I would appreciate any tips on this matter,& please keep in mind I am a bit of a noob so lay terms would be nice!
Thanks in advance!