If you do get attachments regularly, like digital camera pictures, music, funny pdf or Powerpoint presentations or files like that you know the cause for the huge size of your mail folder. It slows down the application as well and it is a good idea to either delete or remove the attachments from the mails by saving them to a directory on the hard drive.

The Outlook Attachment Remover Add-in (via Shellcity) adds the Attachment Remover button to Microsoft Outlook which becomes active after selecting a folder or message.

It removes (detaches) the attachments from the selected mails in Outlook and replaces them with a link to their location on the hard drive. Some alternatives are to keep the attachments or to add a text reference instead of a link to the mail message when removing the attachment.

Two additional filters are available. The first specifies a minimum file size and the second file extensions that will be processed. If you want to detach all document types you use the format .doc;.xls;.pdf;.pps;.

Subfolders of a selected mail folder can be processed and the folder structure can be retained on the hard drive. I was not able to find information about the supported Outlook editions on the website.

The folder size of my Inbox for instance with 100 mails was more than 500 megabytes which could not be true at all. I remembered that Thunderbird did not delete the mails even though they would have been deleted in the trash. This was the cause for the discrepancy between the meager amount of mails and their size and the big huge mail folders on my c: partition.

The solution nevertheless is pretty easy. All that needs to be done is compact the folders which removes all deleted mails immediately. I was able to reduce the folder size of my Thunderbird folders from more than 3 gigabytes to 300.000 kilobytes freeing up valuable disk space on my main partition.

Just right-click a folder and select compact this folder to remove all deleted emails and keep only emails that are visible in Thunderbird. You could check the Disk Space option to automatically compact folders if that saves a defined amount of kilobytes. (You find the option under the advanced tab and offline & disk space tab in the Thunderbird options).