I am receiving emails from Outlook Express warning that I am exceeding 90% of my email allowance. However, there are fewer emails stored within Outlook Express compared with previous times so I do not understand why this message appears. I thought that compacting the Outlook Express folders may resolve the problem, and Outlook Express has been prompting me to compact the folders each time I close the program. However, when I try to compact the folders a message appears saying “The folder is in use by Outlook Express or another application”. Can you advise whether compacting the folders will actually fix this problem, and what compacting the folders will do? The computer is running Windows XP.

I am unsure about the origin of the emails or messages that you are receiving from Outlook Express about exceeding your email allowance, as I have never seen Outlook Express produce such messages (and without further information it will be difficult to say definitely from where these messages are coming). However, from the wording of the email my thoughts are this is not an email from Outlook Express but instead an automated email from your internet service provider warning you that your mailbox on their servers is at 90% capacity and you should remove some messages to free-up space. Before launching into ways to resolve this problem it would be worthwhile to discuss how your email setup (probably) works. Your computer is not always on and may not always be connected to the internet, therefore email messages which are sent to your email address are not delivered directly to your computer. Instead, they are delivered to an email mailbox at your internet service provider (ISP). You can think of this as being analogous to a PO Box at your local post office. When you want to read your email messages you start Outlook Express which then downloads your email messages from your mailbox at the ISP to your local computer. This is analogous to visiting the PO Box and taking your mail back to your home. However, if you do not regularly collect your mail from the PO Box it will accumulate and eventually there will be no more space to put new mail. This is also true for the email system, although if you run out of space in your mailbox at the ISP new mail simply will not be stored and will instead bounce back to the sender (essentially, the mail is returned to the sender), with the reason being that your mailbox is full and therefore the message cannot be delivered into the mailbox.

At this point you are probably thinking that this does not apply to you, since you regularly collect (download) new email and also manage your downloaded email within Outlook Express. However, it is possible that a setting has been enabled in Outlook Express which keeps a copy of all messages on the server. Normally when you download the email from your ISPs mailbox, once the messages have been downloaded they are removed from the ISPs mailbox on the server. In contrast, when this setting is enabled this does not happen, instead when you download email messages from the server a copy of that message is kept on the server. This is useful should you wish to keep a backup of email messages, or download those messages onto another computer, but the downside is slowly over time more and more space is taken-up on the email server to store these messages. Your ISPs mailbox may almost be at capacity, thus warning emails are starting to tell you about this problem. You should be able to tell whether these emails are originating from your ISP since the “From” field in the message will indicate that it was sent from your ISP.

Should these messages be originating from your ISP then we should consider disabling (or at least reconfiguring) the retention of emails on the server once they are downloaded. In Outlook Express, go to the “Tools” menu > “Accounts”. In the Internet Accounts window that appears, click the “Mail” tab. Select your email account in the list and then click the “Properties” button. A Properties window will appear for the email account. Select the “Advanced” tab. At the bottom of the window you should see a section titled “Delivery”. This configures whether messages will be retained on the server after they have been downloaded. You may see the “Leave a copy of messages on server” is ticked. Unless there is a compelling reason why this option is ticked you should untick (disable) this option so that messages are not retained on the server. Click OK to save and close the settings and then “Close” to close the Internet Accounts window. Finally, do a Send/Receive in Outlook Express. This operation will download any new messages from the server and also remove all messages which have already been downloaded, thus reclaiming a significant amount of space which was previously occupied by downloaded messages. From now on, every time you download a message from the server it will not retain a copy on the server.

It is possible that the warning about 90% of your allowance being used is not an email message from your ISP, but instead is a warning message in Windows which perhaps was misread and was actually warning that you have almost used all the hard drive space on your computer and are running out of space. It is important to keep a fair amount of free space on your computer as this is required for Windows to operate correctly, as storage space is required for temporary files and other data for Windows and other programs to function. In this case compacting the Outlook Express folders is a good idea. Each folder in Outlook Express is stored on the computer as a DBX file. This DBX file contains all of the messages that are stored within that Outlook Express folder. When you delete a message within Outlook Express it is not immediately removed from the DBX file, but is instead flagged for deletion. When you compact the Outlook Express folders, all of these deleted messages are then removed. As you can see, if you have deleted a lot of messages then they may have just accumulated in the DBX files resulting in the size of these files growing and occupying more space on the hard drive. Compacting the folders should remove these deleted messages and reduce the size of the files. It is also a good idea to compact the folders as this will reduce the chance of data corruption within the DBX files.

The error message that you are receiving about the folders being in use is a common error. This can usually be resolved by closing Outlook Express then re-opening the program and immediately performing the compaction. It is likely that this has been failing for you because Outlook Express is prompting for you to compact the folders when Outlook Express closes and there may be something happening to the DBX files while the program is closing, preventing the compaction from taking place. However, triggering a compaction manually as soon as Outlook Express opens should get around this issue. Open Outlook Express and then go to the “File” menu > “Folder” > “Compact All Folders”. Once this has completed (which may take a few seconds to a few minutes, depending on how much data needs to be compacted) you should have reclaimed some hard drive space which was previously occupied.

If you continue to receive the message even after compacting the Outlook Express folders it would be worthwhile to check the amount of free space on the hard drive. Go to the “Start” menu > “My Computer”. Right-click on the hard drive and select “Properties”. In the Properties window select the “General” tab and you should see how much free space is available on the drive. If this is very low then you should look at other ways of freeing-up disk space. As a first attempt, you could try running the Disk Cleanup Tool which removes various temporary files from the computer. Go to the “Start” menu > “Run” and type “cleanmgr” (without the quotes) and click OK. Follow through the wizard to clean-up and remove any unnecessary files. Be aware, the wizard will prompt you about which files you wish to delete. I would stay with the defaults to start with (i.e. Downloaded Program Files and Temporary Internet Files) and only proceed to the other options should you need more space, with the exception that I would recommend against the “Compress old files” option – even though this claims to free-up a lot of disk space, the convenience and performance for compressing files is not particularly good.

If all else fails and you need to get more disk space available, you may wish to uninstall programs which you no longer require or consider archiving old documents and files to another source (such as CD/DVD or external hard drive). Of course, you could also consider upgrading your computer to a larger hard drive or, if your computer is relatively old, purchasing a new computer with increased specifications to meet your growing requirements for storage.