PC Win: Using F5 or SHIFT Key to Start Mail Utilities (112265)

This article was previously published under Q112265

Mail message file (MMF) compression and integrity checking are two utilities that are available with Microsoft Mail for Windows. The utilities can be invoked upon Mail startup by pressing F5 for compression and pressing SHIFT for integrity checking.

NOTE: Do not invoke MMF integrity checking unless you know your MMF is corrupted. There is a possibility, depending on the contents of an attachment, that the Mail client will improperly remove part or all of the attachment.

MMF Compression

When a message is deleted, the space it occupied in the MMF is not released. MMF compression reduces the size of the MMF by changing the order of active messages to use the free space left by deleted messages. When the file is compressed, free space at the end of the file is deleted.

MMF Integrity Checking

When the MMF becomes corrupted, it is possible to check and repair it, depending on the type of corruption. Running an MMF integrity check may take a few minutes or several hours, depending on the size of the MMF.