DON'T DELETE THIS MESSAGE -- FOLDER INTERNAL DATA

[iTec Administrator]

From one of our clients email

I recently checked my catch-all email account for the first time and noticed a strange email with the subject line:
DON'T DELETE THIS MESSAGE -- FOLDER INTERNAL DATA

The body of the message says:
This text is part of the internal format of your mail folder, and is not
a real message. It is created automatically by the mail system software.
If deleted, important folder data will be lost, and it will be re-created
with the data reset to initial values.

The message (pseudo-message) is created by IMAP clients that are using the standard Unix mailbox format or the MMDF mailbox format. The file is used to hold information necessary for the IMAP client to manage its persistent unique ID, and settings assigned to the individual mailbox. This is often also used for individual message marking (like "Answered" or "postponed reply") and as settings for creating mailboxes that are designated for postponed messages and the like. If the pseudo-message is deleted, the IMAP client may be unable to determine the mailbox type.