You probably have more add-ins installed than you think. Running unnecessary add-ins may make Outlook slower and even cause stability issues. If the above steps did not help, please try renaming outcmd.dat, extend.dat and Frmcache.dat as described in Part 2 of this article. In addition to PST, OST and profiles, Outlook has several other files which might get corrupted. In this case, you have to create a new profile. Sometimes an Outlook profile might get corrupted. Note: This operation might take a long time if you have a large Exchange mailbox, but you can still use Outlook while it happens.ДЇor a non-Exchange account OST, such as IMAP, use the ScanPST method in the first section of this article. Restart Outlook and let it rebuild the OST file.For example вЂњMary.ostвЂќ to вЂњDELETEME_Mary.ostвЂќ. (It should say вЂњAll folders up to dateвЂќ in the status bar at the bottom of the main Outlook window). To fix an OST file for an Exchange-based account, you simply rename it and let Outlook rebuild it from the server.Д«efore deleting the OST, check that Outlook is fully synced. Note: You can also use scanPST to check and fix your OST files. After you do that, close the old PST file (Right-click the top-most folder of the PST, then select вЂњCloseвЂќ) and start using the new one. In this case, you should create a new PST file and copy all items from the old PST into the new one. ScanPST will tell you that there are no more errors, but you would still experience issues. In some cases, a corruption might be so bad that ScanPST is unable to fix it. Run ScanPST repeatedly, until it reports that there are no more errors.

Important: In many cases, ScanPST requires more than one pass to fix a corruption.

Microsoft is aware of this issue and provides a tool to fix it вЂ“ Inbox Repair tool (scanpst).В Follow the steps listed in that Microsoft Knowledge Base article to run ScanPST. For other account types, follow this section. Follow the next section вЂ“ вЂњCorrupted OST fileвЂќ. If you have an Exchange (or Office 365) account, you have an OST file. Corrupted PST fileД«y far theВ most common reason for Outlook crashes, instability andВ unexplained weird behaviorВ is a corrupted PST orВ OSTВ file. If you are experiencing issues with your Outlook, try these items one-by-one and hopefully one of them will help. This article describes some of the most common reasons that cause Outlook to become unstable, crash, hang or freeze.

Office 365 outlook stuck on processing