Repair PST File

How to fix Outlook Slow? |Outlook 2021, 2019, 2016, 2013 & earlier versions.

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    Summary: Is your Outlook taking forever to receive emails and load attachments? This may be a sign of a damaged PST file or problem with a storage device, such as a hard drive, where the PST file is stored. In this post, we cover solutions to fix this issue Outlook Slow or Outlook Running low performance while sending or receiving emails in Outlook 2007, 2010, 2013, 2016, and 2019.

    Outlook works smoothly when set up on a compatible system. However, with time and as the mailbox (or PST) size grows, Outlook often starts showing signs of degraded performance.

    A most common outcome of this degraded performance and a recurring Outlook issue is that the application starts taking more time to send or receive emails and download attachments. Even after several refreshes, the new emails and attachments are displayed only after a while.

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    Expert’s Opinion: Outlook experts suggest to check the health of Outlook PST file using SCANPST.EXE or a trusted PST recovery softwareIn most cases, error/damage in the Outlook PST file is responsible for the delay in receiving Outlook emails. 

    Read on to know more about the issue. Also, learn solutions to fix the issue of Outlook Running Slow on Outlook 2019, 2016, 2013, 2010 & 2007.

    Why is Outlook So Slow?

    Whenever an email is received in your inbox, Outlook takes the default action of writing it to the PST file. So naturally, if Outlook is taking more time to receive emails, the “writing to the PST” part is the first place to look for possible problems. The problem could be fragmentation or damage to the PST file or an oversized PST.

    A large size PST file is more prone to corruption and hence, you should split PST file or keep backup to avoid Common Outlook errors.

    If that’s the case, Outlook could be spending all its time not in downloading the email but in trying to save it within the faulty PST. So you should focus your efforts on trying to fix and repair Outlook PST to resolve this error.

    How to Resolve Why is Outlook so Slow?

    If emails are taking a long time to arrive in Outlook or Outlook is slow to download emails and attachments, try the following solutions to get rid of the problem:

    Backup the PST file before applying these solutions.

    1. Check hard drive for bad sectors

    In case your hard drive has developed bad sectors and your PST file is stored at a location on the hard drive that includes one of those sectors, it could be a cause of this Outlook Running Slow.

    Thus, as a first step, use a tool such as CrystalDiskInfo and check hard drive health status and SMART information. Make sure drive health is good and there are no Reallocated Sector Count warnings.

    You can also run a Check Disk command in Command Prompt window. Close all programs before running the following command.

    CHKDSK /r
    Check Disk Command in Command Prompt

    Type ‘Y’ and press ‘Enter’ if asked to force dismount volume.

    The CHKDSK command will find out and repair hard drive errors. After this, restart the system and open Outlook. Try sending a few emails and check if Outlook sends/receives emails normally.

    2. Defrag the hard drive

    Disk fragmentation is a process that occurs naturally, as files are constantly being written, edited, deleted, and resized. When a large file is spread across several locations on the drive, it takes much longer to read and write.

    And it’s quite possible that your PST file may be fragmented and that’s why Outlook is so slow to load emails and attachments.

    So defragmenting your hard drive would be a good idea here if you haven’t done it recently. To defragment, simply type ‘defrag’ in search and click on Defragment and Optimize Drives.

     type defrag in search and click on Defragment and Optimize Drives.

    Select the drive volume where your PST file is stored and click ‘Optimize’.

    Select the Drive where PST file is stored and click Optimize
    Also, optimize other partitions and then check your Outlook.

    If the drive isn’t fragmented or Outlook is still slow to receive emails, head to the next solution.  

    3. Compact or Compress Outlook PST

    As mentioned earlier, a large PST could also cause Outlook Running Slow. Defragmenting your hard drive also squeezes out unnecessary empty spaces from within the PST that might have been created due to regular email deletion/moving.

    Further, you can compress or compact the Outlook PST file. Compacting the PST file size helps keep a check on growing PST size. To compact Outlook PST:

    1. Launch Outlook
    2. Right-click on Personal Folder or Outlook PST
    3. Click on Properties -> Advanced 
    Go to>Personal Folder>Click on Properties -> Advanced
    Check ‘Compress contents to save disk space’ box and click ‘OK’, then ‘OK
    Check Compress contents to save disk space’ box and click OK, then OK

    Compacting of the PST is a time taking procedure depending upon the PST file size. You might have to leave it to run overnight.

    4. Disable Faulty Add-in

    An incompatible or faulty Add-In may also cause Outlook Slow & delay in receiving and loading Outlook emails and attachments. Follow these steps to find the faulty Add-in and disable or uninstall it.

    • Go to Outlook Options -> Add-ins -> Go in Outlook 2007 or 2010. In Outlook 2013 and later, go to File>Manage COM Add-Ins. This opens up a dialogue box listing all installed add-ins
    • Uncheck all Add-Ins names to disable them
    Outlook Options -> Add-ins -> Go in Outlook 2007 or 2010. In Outlook 2013 and later, go to File>Manage COM Add-Ins
    Now try to send/receive or reply / forward messages and check if it works

    Enable each plugin one-by-one and check Outlook. This will help you find the Add-In that is creating the problem.

    To Troubleshoot Outlook Performance Issues Manual Guide

    5. Repair PST

    If none of the above solutions works, you would have to explicitly repair Outlook PST to fix the issue. Microsoft ships an Inbox Repair Tool with its MS Office suite. This utility finds and repairs minor faults within the PST file and make it workable again.

    Locating Scanpst.exe utility in WIndows Outlook

    You can find this utility within your Outlook installation folder. Double-click on SCANPST.EXE to launch the Inbox Repair Tool and browse the PST file. Then follow the wizard to repair it.

    Repairing PST errors with SCANPST.exe tool

    However, if for some reason ScanPST.exe cannot fix the faulty PST, you don’t need to despair. Use Stellar Repair for Outlook—an ultimate solution to resolve PST and Outlook errors.

    This automated and user-friendly software is equipped with algorithms dedicated to resolving minor as well as major PST corruption issues. It can even let you perform advanced tasks such as compressing PST, splitting it, etc.

    Stellar Repair for Outlook to fix PST error and corruption

    Final Words 

    Once you have fixed the Problems such as ‘Outlook slow’ issue using the solutions mentioned above, defrag your system once more. This is to ensure that whatever data was moved around to rectify the Outlook PST error is placed back where it belongs, safe and sound.

    If you’re still facing Outlook Running Slow, Outlook is Slow, leave a comment or reach us via the Support page.

    Similar Links:

    How to compact PST

    How to find Scanpst

    Free Ways to Repair Outlook PST File

    Outlook 2016 running Slow on Windows 10

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    About The Author

    Eric Simson linkdin

    Eric Simson is an Email Platform Consultant and is associated with Stellar Data Recovery from last 6 years. He writes about the latest technology tips and provides custom solutions related to MS Outlook, MS Exchange Server, Office 365, and many other Email Clients & Servers.


      1. Hi sfmitch,

        The default PST file size limit in Outlook 2019/2016/2013/2010 is up to 50 GB. In Outlook 2007/2003, the default PST file size is 20 GB and 2 GB in Outlook 2002 and lower versions. If the Outlook data file (.pst) size exceeds the default size limit, you may encounter issues in Outlook, such as the slow receiving of emails.

        However, it is important that you run ScanPST.exe tool once in a while to check for errors in a PST file. That is because PST files start developing integrity issues as they store more data and its size increases.

    1. Hi Eric,

      we have problem about sending email.when I rigt-click on file and then send email, the email is wiaiting in outbox.but when ı open the outlook, after 15-20 seconds the mail sent.

      why can’t email send when the oulook close?


    2. In our case, Outlook 2013 is very slow for downloading emails. I did all manipulation but no improvement in downloading speed.

      Please guide!

      1. You should also check the size of PST file. A heavy-sized Outlook data file is responsible for decreasing performance in Outlook.

    3. Since I had recently installed the hard drive the possibility of bad sectors was nil so I skipped running the disk check, however even compact and repair PST file were unsuccessful.
      Do you think Stellar PST Repair would able to quicken me Outlook 2016 client?

      1. Have you tried ScanST.exe? If no, then try this one freeware PST repair tool and share your experiences with us.

    4. I have encountered this one error after Windows 10 update. For time being, I can operate daily activities in Outlook but wish to have speedy performance.

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