Mail Folders

A mail folder is a collection of mail messages stored in a single file. By convention, all folders are stored within a directory called $HOME/mail or $HOME/Mail (directory mail in the user's home directory).

A folder is usually referred to as

+folder_name or =folder_name

where the plus (+) sign means that the file is residing (or is to be residing) in the folder directory ($HOME/mail). Note that that convention does not hold for all mail clients; some require the mail folder directory be included with the folder name.

The default folder is the user's system mail folder, /var/mail/user.