Reducing the size of IMAP folders in Outlook involves managing your mailbox by archiving, compacting, or deleting items. Here’s a step-by-step guide on how to do this:

Option 1: Archive Emails:

1. Open Outlook: Launch the Outlook application on your computer.
2. Go to the File Tab: Click on the “File” tab at the top-left corner.
3. Choose “Options”: Select “Options” from the File menu.
4. Access Advanced Settings: In the Outlook Options window, click on the “Advanced” tab.
5. Click on “AutoArchive Settings”: Under the “AutoArchive” section, click on “AutoArchive Settings.”
6. Configure AutoArchive: Set the options for AutoArchive based on your preferences. You can choose to archive old items to a separate PST file.
7. Apply Changes: Click “OK” to apply the changes.

Option 2: Compact Folders:

1. Go to the File Tab: Click on the “File” tab at the top-left corner.
2. Account Settings: Under Account Information, click on “Account Settings” and select “Account Settings” from the dropdown.
3. Data Files: In the Email tab, select your IMAP account and click on “Settings.”
4. General Tab: In the Email Account window, go to the “General” tab.
5. Click “Compact Now”: Click on “Compact Now” to reduce the size of the selected data file.

Option 3: Delete Unnecessary Emails:

1. Open Outlook: Launch the Outlook application on your computer.
2. Navigate to the Folder: Go to the IMAP folder you want to reduce in size.
3. Delete Unnecessary Emails: Delete unnecessary emails by selecting them and pressing the “Delete” key.
4. Empty Deleted Items: Right-click on the “Deleted Items” folder and choose “Empty Folder” to permanently delete the items.

Note:

1. Archiving moves items to a separate file, reducing the size of your main mailbox.
2. Compacting folders removes unused space in the data file.
3. Deleting items frees up space immediately, but ensure you’ve backed up important data.

Remember, these steps may vary slightly based on the version of Outlook you’re using. Always back up important emails before performing actions that involve deletion or archiving to avoid accidental data loss.