.ost file considerably larger than Exchange Mailbox.

[Guest]

I have an Exchange Mailbox that has 675Mb in it. The new .ost file is 695Mb.
The old .ost file is 1.46Gb. The largest the mailbox ever got to was 1Gb. I
need to see what data is in the old .ost file, however when I choose to work
offline the folder sizes don't change. I can switch between the .ost files
and still the file sizes are the same. I don't understand why there is such a
large difference in size. If anyone has any information on this, it would be
greatly appreciated.

 

[neo [mvp outlook]]

The compression used in OST files is not as efficient as what Exchange can
do, so having an OST file that reads a bit larger than the actual size is
fine. The other thing about OST files is that they are like PST files in a
sense that they don't shrink in size and that there is always some
whitespace. So having a 1.46 GB file means that Outlook doesn't have to
grow the file excessively fast if you get a burst of messages that need the
extra space.

If you are really worried about the size and want to compact the OST file,

advanced button > advanced tab > offline settings > compact now.

Oh and in regards to your other post. If you are running in cached mode,
you are primarily working out of the OST when working with folders in our
mailbox. As soon as you jump to a public folder, Outlook switches to a
traditional "online" connection like Outlook 97/2002.