0 Reduce size of Outlook data file.

Outlook data file may grow big. I mean really big.
If it's size is defined in Exchange server, then by reaching it's quota it wont receive any email.

You can handle this problem by:
---------------------------------------------------
Manage the size of your mailbox

You can use the Mailbox Cleanup tool, which allows you to view the size of your mailbox and individual folders. You can also archive older items to an archive Personal Folders file (.pst) and empty your Deleted Items folder.

On the Tools menu, click Mailbox Cleanup.
Do any of the following:
To view the total size of your mailbox and of individual folders within it, click View Mailbox Size.
To locate older items, select Find items older than n days, enter a number between 1 and 999, and then click Find.
To locate large items, select Find items larger than n kilobytes, enter a number between 1 and 9999, and then click Find.
To move older items in your mailbox to an archive Personal Folders file (.pst), click AutoArchive. The default folder for archive .pst files is c:\Documents and Settings\user name\Local Settings\ Application Data\Microsoft\Outlook.
To view the size of your Deleted Items folder, click View Deleted Items Size.
To empty your Deleted Items folder, click Empty.
To view the size of your Conflicts folder, click View Conflicts Size.
To delete the contents of your Conflicts folder, click Delete.
---------------------------------------------------
1.Reduce the size of a Personal Folders file (.pst)

If you delete items from a Personal Folders file (.pst), the file is automatically compacted in the background when you’re not using your computer and Outlook is running. If you want to immediately reduce the size of the file, you can force a compaction. The procedure to compact the data file might take several minutes.

On the File menu, click Data File Management.
Click the data file that you want to compact, and then click Settings.
Click Compact Now.
NOTE You do not have to exit Outlook after you compact a .pst file.
---------------------------------------------------
Reduce the size of the Offline Folder file (.ost)

Reducing the size of the Offline Folder file (.ost) file may improve performance if you have deleted a large quantity of items. This procedure does not delete any items that are saved on the server.

Delete any items that you do not want to keep, and then empty the Deleted Items folder.
On the Tools menu, click Account Settings.
The Account Settings command is missing.

In the list, select Microsoft Exchange Server, and then click Change.
Click More Settings.
Click the Advanced tab, and then click Offline Folder File Settings.
Click Compact Now.
---------------------------------------------------