Microsoft Outlook is likely the most widely used email program for Windows, but Outlook has a serious flaw that most users have no clue even exists. What if you had years worth of important emails stored in Outlook and they simply disappeared one day? It can happen.
Outlook stores your emails, contacts and calendar data all in one big file. Typically that file is called outlook.pst and is located in the hidden folder C:\documents and settings\*Your Username*\local settings\application settings\Microsoft\Outlook.
The problem is that this file has a 2 gigabyte limit. Once the file grows beyond that size, you are at serious risk of it becoming corrupted and losing all your data.
This problem leads to two questions. First of all, how do I tell how large my PST file is? Click on Start, then run and enter the path "C:\documents and settings\*Your Username*\local settings\application settings\Microsoft\Outlook" then click ok. Be sure to replace "*Your Username*" with your own username. You can also browse to it in Windows Explorer, but a few of the folders are hidden, so you have to click on "Tools", "Folder Options", "View", then select "Show hidden files and folders", click "Apply to All Folders" and then "OK". Once you are in the Outlook folder, you can locate your Outlook.PST file. Now right-click it and click properties to open its properties sheet. Here you can see the file size. If you are approaching 2GB, you need to address it.
So... how to make the PST file smaller? PST files often contain empty space left over from deleted emails and other objects. When you delete emails, the file does not shrink. You have to compress it. To do this, find "Personal Folders" in the folder view on the left side of Outlook. You may have to click on "View", then "Folder View" to see it. Also, you may have renamed "Personal Folders" to something else. Right click on it and then left click on "Properties". Now click on Advanced, and then click "Compact Now". This may take up to a few hours to run. This process removes any empty space from the PST file.
If the PST file is still too large after you have compressed it, then you need to remove some emails and compress it again. Be sure to delete old emails from the "Sent Items" folder and the "Deleted Items" folder. If you really must keep every email that you have, then you should archive older emails off to another PST file. Having two 1GB PST files is okay. Having one 2GB PST file is not.
Outlook 2003 has an easy to use "Auto Archive" option. Click on "Tools", "Options" then "Other". Now click the "Auto Archive" button, choose your options and click OK. Click OK again to close the options screen. After the Auto Archive has run, be sure to repeat the "Compress" process above and then recheck the size of your PST file.
This information will allow you to use Outlook for years without losing all your emails. Of course now that you know how to find your PST file, it's the perfect time to back it up.