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E-mail mailbox format change

Date: January 2008

What changes are being made?

Because desktop email programs do not interact directly with mailboxes, the change to the MIX mailbox format will not result in any visible change for most programs.

During this fall, CNS Network Services will be changing the format used for email mailboxes (sometimes called "folders") on the UTORmail systems from UNIX and MBX to MIX. Because email clients connect to the IMAP email server, which in turn interacts with the folders, for most users this change will not be visible.

What will users of UTORmail see?

For most users, the change should have no visible effect other than greater speed in accessing mailboxes and messages. However, because of variations in how email clients work, users may see some of the following behaviors:

• When users first connect after the change, they may experience a delay or see messages as their email client synchronizes with the new configuration. This should be a one-time event.
• MIX makes possible creating sub-mailboxes within mailboxes, but not all email clients are capable of creating sub-mailboxes.
• With the Pine family of email clients (Pine, UTORwebmail, PCPine, and Alpine) mailboxes containing mailboxes have a slash before their name.

No changes are needed in the configuration of email clients.

Why make the changes?

The change in mailbox format is being made for the following reasons:

• Much faster performance compared to the old format
• Greater robustness against corruption caused by hardware or software failures
• Much easier to repair should corruption occur
• New capabilities for having mailboxes within mailboxes, for those email clients that support them
• Compatibility with new IMAP capabilities soon to be available
• Lower system overhead for system backups

When will the changes be made?

Most email accounts will be converted to the new format during the late summer. The change will be announced in advance through the NWADMINS/ut-admins lists and in an article on the UofT Homepage, portal.utoronto.ca and news.utoronto.ca.

What is the difference between MBX and MIX

In the old MBX format, a mailbox and the messages it contains are all written in a single file, the contents of which are accessed with random-access reads and writes.

the MIX format manages an email mailbox as files within a directory, with each file containing a particular type of information about the mailbox. Examples of such information are metadata about the mailbox, an index of messages, data on message status, and the messages themselves, each type of information in a separate file.

With MIX, the directory containing a mailboxes' information and contents can also contain a subdirectory that holds the contents of a sub-mailbox (a mailbox within the mailbox). Such directories set up to store messages and subdirectories are called "dual-use mailboxes" since they are both a mailbox (containing messages) and a directory (containing sub-mailboxes).

More information

• MIX Format Description