Microsoft KB Archive/105109

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PC Win: .MMF File Size Increases by Twice the Size of Message

Article ID: 105109

Article Last Modified on 10/30/2006


  • Microsoft Mail Client 3.0
  • Microsoft Mail Client 3.0
  • Microsoft Mail Client 3.2

This article was previously published under Q105109


With versions 3.0, 3.0b, and 3.2 of Microsoft Mail for Windows, the size of a Mail message file (MMF) may increase by more than twice the size of a message received.

Additionally, if the sender of the message selected the Save Copy Of Outgoing Message In Sent Mail Folder option, the sender's .MMF file may also increase by more than twice the size of the message sent.


The receiver's .MMF file may increase by more than twice the size of the received message because as soon as the message is opened for reading, a temporary (duplicate) copy is created. This duplicate is the size of the original message. This temporary copy is created to allow the user to modify the message received and then be given the Save Changes To Message? option. This process allows the user to discard any changes and restore the original message.

On the sender's side, a message is created for sending. When the message is sent, a copy is made and is put into the Sent Mail folder. The original message then is deleted. Thus, two copies of the message were created, and space had to be allocated for both these copies. Even though the first copy of the message was deleted, the space is only logically freed. Until the .MMF compression runs, the space occupied by the first message will not be physically freed. This is done so that if another large message (or a set of messages) is sent or received, the program will be able to work faster, because it already has the disk space allocated.

Additional query words: 3.00 3.00b 3.20

Keywords: KB105109