E-mail “Inbox” files
(...or, Why you should not delete “mbox”)
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The default “Inbox” or “INBOX” folder you see in your E-mail client consists of two components on the mail server. Incoming mail which a user has not downloaded or looked at yet is stored in a separate E-mail spool area, which is not subject to the user's home directory file space quota.[note 1] On the P-A E-mail server, each user's file is called /var/mail/username. As soon as a user connects with an E-mail browser, or issues a “get new mail” command from within the browser program, the contents of /var/mail/username are moved to the file representing the second component of the “Inbox” concept. This is the file “mbox” in the “mail” subdirectory of the user's home directory [note 2]. Any incoming mail which has already been retrieved and/or looked at by a standard E-mail browser [note 3] is now in this “mbox” file in the user's file space, and is now subject to the user's file space quota. [note 4] This scheme has some side-effects. One is that if an incoming E-mail message is large enough that it would push your file space over your quota, then the contents of /var/mail/username are not moved to the mbox file when an E-mail browser programs requests it. Some E-mail browsers will still let you see these new messages, even if they remain in /var/mail/username (i.e., they treat “Inbox” as the union of the two files), while others will not (i.e., they seem to believe that, since the command to move the mail contents to the “mbox” file was issued, that's the only file they need to deal with). If this happens, delete enough files to free up the necessary space and/or contact helpdesk@pa.msu.edu to have your quota increased. Another side effect is that users have a separately-listed “mbox” folder, which appears to have the same contents, in most situations, as their “Inbox” folder. This is no real problem: ignore it or just treat it as an alternate way of seeing “Inbox” contents. If your E-mail browser is among the better-designed ones, it will have an option something like “show only subscribed folders”. If this is set, you can unsubscribe from the “mbox” folder and, even though it is there on the server, you will not see it as a separate entry in your folder list. If you delete your “mbox” folder, all your “Inbox” mail is gone! [note 5] |
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Notes: 1. If SpamAssassin has been installed for a user, there will be additional “inboxes”, all of which are in the user's own “mail” subdirectory, as “mbox” is, and are therefore also subject to file space quotas. If the quota is exceeded, the E-mail which would ordinarily go into one of the separate spam “inboxes” such as “IN.spam” may end up in /var/mail/username instead. 2. On our server, there also has to be a “link” to this “/home/username/mail/mbox” file in the “/home/username” directory. If this link (or the underlying “mbox” file it points to) is missing, the movement of message contents from /var/mail/username to /home/username/mail/mbox will not work. 3. Such E-mail browsers include the text-mode “pine” client on the mail server and IMAP-compatible E-mail browsers such as Outlook Express, Outlook, Apple Mail.app, Eudora and Mozilla (including variants such as Thunderbird and Netscape). 4. There are utilities which look at /var/mail/username without moving its contents to /home/username/mail/mbox, but most users will rarely if ever use them, so if you don't already know about them, don't worry. These include the Unix/Linux command-line “mail” command and programs designed to alert users to new mail without actually trying to read it (such as “xbuffy”). The latter function is handled automatically by the better-designed E-mail browsers mentioned in note 3. 5. User areas on the mail server are backed up once a week (generally alphabetically, so “a*” user areas are backed up Monday evenings and “z*” user areas are backed up Friday evenings, and the others are in between). Depending on your timing, deleting “mbox” may lose you up to a week's worth of mail that has not been filed away into other folders yet. |
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