Compress Outlook Data Files

If you use Outlook, it’s a good idea to compress your Data files from time to time – especially if you’ve had an email clear-out. Even if you haven’t, it a good practice to follow

As you receive more mail, your email Data File grows. Deleting mails itself, doesn’t generally reduce the size of these data files, and they can run into gigabytes in size. There is a simple exercise we can do to bring the size back down to earth.

There are two types of mail data files – .ost & .pst

.OST (OfflineSTorage) is usually for IMAP & Exchange accounts (eg, your corporate email file), and .PST (PersonalSTorage) for pop3 accounts – including (in most cases) any archive files you’ve created.

To see all your data files (Office 2010)…

FileàAccount SettingsàAccount SettingsàData Files tab

This will list your data files. In the Location field, look at the last 3 characters to see if you’re using pst or ost. The procedure is very similar, but a couple of different clicks.

When you’re ready to go ahead, select the data file, and click ‘Settings’

PST Files

You will immediately see a ‘Compact Now’ button – click it and wait!

On large pst files, this can take some time (about 20-30 mins for my 9gb file)

OST Files

After clicking the ‘Settings’ tab, you will instead see a different set of options. Select the ‘Advanced’ tab

Then click ‘Outlook Data File Settings’

And select ‘Compact Now’

This is invariably faster for me than compacting my archive folder, given my mail Exchange account has a size limit attached (hence needing an arxhive folder!). Nonetheless, it can take a few mins to complete

That’s you done. You shouldn’t need to do this too often – perhaps a few times per year, but is a good routine to stick with.

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