Managing the folder garbage collection threshold

Garbage collection only occurs when a folder is closed, which includes disconnecting from the IMAP and POP servers. At that time the threshold is checked and garbage collection is performed if necessary. Set a threshold value in order to determine when the copy and rewrite operation occurs. This threshold saves time, as the copy and rewrite operation has to be performed less often and the folder (message store) marks messages as deleted.

A 100% threshold means that 100% of the bytes in a folder are kept valid. A 50% threshold, for example, means that a garbage collection operation will take place on the next close (after enough messages have been marked as deleted), so that the number of bytes in the undeleted messages drops below 50% of the final size.

A threshold of less than 100% provides substantial performance gains when used with POP and IMAP clients, as their operations become lightweight. It reduces the frequency of garbage collection, which is an expensive operation for large folders. The default value is 50%.

Setting the garbage collection threshold to 0 (zero) means that garbage collection will never be performed, hence the INBOX will grow but never shrink.

To change the threshold:

1. Double click on the ``Folder Garbage Collection Threshold'' entry to produce a pop-up ``Modify Folder Garbage Collection Threshold'' screen.

2. Enter a number between 0 and 100. An error message is displayed if you enter an invalid number.

3. Click on OK to return to the main screen.