To solve this, select each PST file (usually called Outlook or Personal Folders), right click on it and choose Data File Properties > Advanced > Compact Now. When something is deleted, it is left for a long time before it is actually deleted from PST file. Outlook is not very efficient with PST file space. This makes Outlook download whole emails to your computer, not just headers, so it should be much faster. Select each account on the left and make sure that “Download complete items including attachments for subscribed folders” is selected. Go to Send/Receive tab, Send/Receive Groups, Define Send/Receive Groups, select All Accounts and Click Edit.
Just launch it and deselect add-ins that you do not use. No need to dig into Outlook configuration here, since we do have a free application just for this job – EnableDisable for Office. This step probably is the most effective, since unused add-ins can really slow down your Outlook. TIP: Latest version of Deduper for Outlook allows to remove duplicate emails automatically with a single click.
