XCLN: Comparing MMF and PST File Sizes

The information in this article applies to:

• Microsoft Exchange Windows 3.x client, version 4.0
• Microsoft Exchange Windows 95 client, version 4.0
• Microsoft Exchange Windows NT client, version 4.0

SUMMARY

If you used Microsoft Mail before migrating to Microsoft Exchange, you might have message files (MMF files) that you want to move to Microsoft Exchange. To do so, you must convert the information from its original format to a PST file. You can then add this file to your active profile. To see the steps to import an MMF file, please see the Microsoft Exchange Client Help topic on Importing MMF files. This article discusses the file size differences between MMF and PST files.

MORE INFORMATION

MMF Smaller than PST:

When an MMF file is converted to a PST file, the size difference will be noticeable. The PST file will usually be larger than the original MMF file. This is due to the way that PST files store Compressed RTF and Message Body for each message. MMF files only store Message Body format and not the Compressed RTF format.

MMF imported into Microsoft Exchange Mailbox Folder:

Migrating the same MMF file to a Microsoft Exchange Server Mailbox folder will cause less data to be stored on the Microsoft Exchange Server. This is because it only stores the RTF part of the message and it is compressed. Compressed RTF is usually smaller than the original plain-text body.

PST Smaller than MMF:

A non-compacted MMF file that is converted to a PST file can actually yield a PST file that is smaller than the source MMF file. In addition, if the source MMF file has corrupt messages in it, those messages will be deleted by the migration utility, resulting in a smaller PST file.

TIP: To reduce the size of your MMF file, discard messages that you no longer need and compact the file before importing it.

PST encryption is a direct byte substitution for the original data, so a PST file with encryption will be the same size as an otherwise identical PST file without encryption.