kmail: Overstuffed Mailbox Issues

Overstuffed Mailboxes -- Prevention

There are serious issues that can develop when mailboxes become "overstuffed" -- this applies to mailboxes and possibly to folders of mailboxes that grow to sizes approaching 1 GB. It is not necessary to reach that size, however, and care should be exercised for any mailbox with thousands of messages and requiring even hundreds of MB. Mailboxes can grow in size, primarily because of large attachments stored as part of the message archives.

First read the support document at:

Mac OS X 10.3 Mail: Overstuffed mailbox is unexpectedly empty

Note: the Home directory (~/)

It is conventional to use the tilde (~) character to represent the user's Home directory. The Mail application stores email data in ~/Library/Mail.

The issue occurs when Mail is indexing a large mailbox, and might also arise when viewing a blend of several large mailboxes in a folder of mailboxes. (For a mailbox with thousands of messages you may have seen Mail's performance during access slowed, because of the number of items being indexed.) It is good practice to create new mailboxes periodically, and to transfer messages to them, perhaps based upon time period or subject area. Mailboxes of 100 MB or less should be quite efficient to use. In addition, in Panther, there is the option to remove attachments from email messages, usually after storing the attached files in an ordinary folder outside of Mail -- this option is not available in 10.2.8, and earlier versions of OS X.

The size of mailboxes can be observed in two ways:

1) In Mail, when the mailbox is open, view the size of the mailbox in the Status Bar above the list of messages. To enable the Status Bar, see:

Mac OS X 10.3 Mail: Checking the size of a message or mailbox

2) in the Finder, open ~/Library/Mail and observe the mailboxes you frequently use, with Get Info. This would include Inbox and Sent Message mailboxes in each Account folder, and any in the Mailboxes folder (where On My Mac mailboxes created by the User are stored).

While in the Finder, if you have mailboxes now in Panther Mail, but that originated in Jaguar, then Control-Click over each one, and choose Show Packages Contents. Observe what files are contained in addition to content_index, tableofcontents, info.plist and mbox. Any containing SKindex in their name may safely be deleted if versions earlier than 10.3 will no longer be used -- this is recommended, since these left over files can become problematic at times. If the mailbox has been opened immediately prior to observing the package, no other files should be present. If any others are observed, use the Discussion Forums to seek advice.

Overstuffed Mailboxes -- Salvaging Messages

If you have a mailbox that has become inaccessible due to being "overstuffed", you should consider upgrading to OS 10.3.4, or higher. The Mail application in these versions of OS X should be able to access the overstuffed mailbox, but may require some actions on your part to complete.

If, after upgrading the 10.3.4, or higher, the mailbox will still not open (or complete its indexing), then from the Mailbox menu, choose Rebuild.

If the mailbox continues to be inaccessible, then take the following actions:

First, quit the Mail application.

To protect yourself, make a temporary backup copy of your email data. In the Finder, select the ~/Library/Mail folder. From the File menu, choose Duplicate and drag this copy to your Desktop.

If the mailbox is an Inbox, or the Sent Messages mailbox in an Account folder, see the ADDENDUM at the bottom of this FAQ.

Next, Control-Click over the overstuffed xxxx.mbox file, and choose Show Package Contents -- delete all files in the package, EXCEPT the file named simply "mbox". Relaunch Mail, and click to open this mailbox, and wait for Mail to complete re-indexing of the mailbox. When you first open the mailbox, Mail will use a great deal of time to read through the mailbox and all the messages in the mailbox will be marked as unread. If you click on Edit and choose Select All, then all messages will be highlighted, and if you then click on Message, you can choose to Mark all as Read. Then click on one message and the highlighting disappears. At this point you should be back to normal.

If after these steps the mailbox does not open or complete indexing, select the mailbox and choose Rebuild from the Mailbox menu again.

If none of these steps succeed (or you will not be using 10.3.4 or higher), then do not remove or delete the xxxx.mbox file, but rather post to the Discussions for further assistance -- there are other techniques to consider for salvaging your messages in the mailbox.

ADDENDUM:

If the mailbox is an Inbox, or the Sent Messages mailbox in an Account folder, you might consider taking actions to allow you to return full use of the Mail program while you resolve this issue. To do this, you should quit Mail and open the Account folder in the Finder (~/Library/Mail/email-account folder) and drag the mailbox (INBOX.mbox or Sent Messages.mbox) from the account folder to the Mailboxes folder of the Mail folder, taking care to rename if any by that name exists in the Mailboxes folder already. After doing this, relaunch Mail, and the mailbox you moved will be recreated in the account folder when needed.

If you do not move an overstuffed INBOX.mbox from its account folder, then in Mail Preferences, Advanced setting should deselect "Include this account when automatically checking for new mail". When you have completed your efforts to regain access to the Inbox, then change the setting in Advanced to again check for new mail, use Rebuild Mailbox for good measure, and test performance.