how to filter email

[pickett]

How do you block email from certain domains (ie @blah.com) in 
Slackware?


Reg Pickett                 Work: +06 7 4939 9414
Computer Technician      Home: +06 7 4938 3817
St Brendans College       Mobile: 0414 950 415
Mary's Mount
Yeppoon Q 4703