procmail - 3.22-27 main

Can be used to create mail-servers, mailing lists, sort your incoming
mail into separate folders/files (very convenient when subscribing to one
or more mailing lists or for prioritising your mail), preprocess your
mail, start any programs upon mail arrival (e.g. to generate different
chimes on your workstation for different types of mail) or selectively
forward certain incoming mail automatically to someone.