Question: Why is it important to set the IMAP mail prefix?
Author: Joseph Tam
Date: Apr 5, 2012
(This FAQ is obsolete: the IMAP server now converts blank or unset mail
prefixes to the correct satting.)
The IMAP mail prefix -- also called path prefix,
personal mail folder or server directory -- is a setting
that states where all your personal mailboxes are stored. Our webmail system and Unix
mail reader pine, uses the following setting
IMAP prefix = mail/
This should also be your setting.
It is important not to leave this setting blank; if you do, this
will make the IMAP server assume that all files in your home directory
are mailboxes. The IMAP server will then attempt to process all files
in your home directory as mail resulting in very slow mail access.
The IMAP server will also consume gobs of memory.
The following clues are indicators that you have not set the
IMAP prefix correctly:
- You have mailbox files at the top level of your
home directory e.g. "Trash", "Sent Mail", etc.
- The list personal mailboxes you see from your IMAP mail
reader is different than the list you see from pine or our
- You can see lots of files in your personal mail folder
that are not mailboxes, such as dot-files like ".cshrc" and
".login" or other files you have created.
Setting the IMAP prefix correctly will improve the performance
of your mail reader.
Caveat: if you change the IMAP prefix from blank to the proper
setting, some of your personal mail folders will seem to disappear.
This is because IMAP is now confining itself to the mail folder as it
should, and therefore, cannot see the other folders that were erroneously
put at the top level of your home directory. To avoid this situation,
you should move these mailboxes into the correct place (within the mail)
directory before you correct your mail prefix. You can do this either
through the Unix command line interface
mv mailbox1 mailbox2 ... mail
or you can use the mail reader to move mailboxes into the mail subfolder.