How-To Fix Outlook 2007 Slow Performance Issues

When I upgraded to Outlook 2007, I began to use the built-in Instant Search, and I found it wasn’t that INSTANT. Not only that, Outlook 2007, in general, was just plain SLUGGISH.

The culprit turned out to be my use of large.OST and .PST files. Luckily for me, I was able to find the fix.  Additionally, I was having severe performance issues with the Outlook AutoComplete function.  Anytime I typed something into the TO: line or CC: line, my Outlook client froze while looking it up in the AutoComplete.  Right when I was ready to uninstall Outlook 2007, I figured out the solution.

Anyway, back to the slow Outlook 2007 performance Fix:

Microsoft posted a fix: Update for Outlook 2007 (KB933493)

This update fixes a problem in which a calendar item that is marked as private is opened if it is found by using the Search Desktop feature. The update also fixes performance issues that occur when you work with items in a large .pst file or .ost file.


FYI, on a performance note, Microsoft just released a few Windows Vista updates, which could improve the performance of Outlook 2007 running on Vista.  Take a look here.



  1. JC

    August 20, 2007 at 6:01 am

    Did this fix actually work for you? My outlook 2007 is still very slow ever after applying this hotfix. Even worse, I often get warnings that say outlook was not closed properly and a data file check is performed. That slows down the entire computer!

  2. MrGroove

    August 23, 2007 at 9:05 am

    Hi JC,
    For me personally, yes. This patched fixed “one” of the problems I was having which was a slow instant search experience which was a direct result from having a really large OST and PST attached to my outlook profile. It’s not however a silver bullet for the slow outlook 2007 performance.

    If your still having problems my recommendation would be to post your questions in our Microsoft Office forum so the entire community here at groovyPost can assist.

  3. David

    September 20, 2007 at 7:41 am

    My issue with Outlook 2003 on vista was it would become unresponsive while navigating the e-mail structure. Task manager showed that Outlook was using very little resources (processing time). After reading other posts on the internet, I decided to disable my Symantec Antivirus Client from scanning e-mail, and Voilla! Outlook functions again. I’m not sure why this works, and I’m not happy that I must disable my e-mail scanning, so I cannot tell everyone to do so. However, I have contacted Symantec about this issue and hope they will work to resolve it.

    Cheers. David

  4. MrGroove

    September 20, 2007 at 4:56 pm

    Hi David and Welcome to the site!

    I had similar issues with McAfee as I stated here:

    How that was associated with the “Auto-Complete”. Not suprised that Symantec or even McAfee for that matter is causing Performance issues. I think were going to be seeing a lot of tuning from AV agents as they become familiar with Vista and Outlook / Office 2007.

    Thanks for the contribution!

  5. RuFo

    November 23, 2007 at 2:24 am

    Outlook 2007 was also extremely slow – moreso when opening an email. What worked for me was – Tools|Trust Centre|Attachment Handling – Check the box to “Turn Off Attachment Preview”. This sped up opening of emails.
    I am however still having a slow response when opening an Office 2007 attachment. Troubleshooting that right now.

  6. MrGroove

    April 10, 2008 at 9:47 am


    Thanks for the additional Tip RuFo and WELCOME to the site!

  7. tig

    June 6, 2008 at 12:18 am

    rufo, I just applied the hotfix, and opening emails was a bit sluggish.
    Checking the box to “Turn Off Attachment Preview” seems to speed things up …. thanks

  8. Montan

    July 4, 2008 at 8:57 pm

    This is what worked for me. I have a roadrunner email account running on Outlook 2007. All of the sudden send and receive mail was slllooowww. I logged into my Roadrunner web-based email mail account and found over 100 junk mail messages that existed even though I had deleted them from Outlook. I deleted them on Roadrunner web email and my Outlook was magically fixed. Hooray!

  9. Robby Slaughter

    July 10, 2008 at 6:44 am

    Here’s a workaround which is *amazingly* effective for me. When Outlook 2007 on Vista freezes up when trying to save a contact or an appointment or send an email, go to the icon in the bottom right corner of the taskbar and right click. Select “Cancel Server Request.” Works perfectly!

  10. Darren

    August 17, 2008 at 3:51 pm

    Well, if you ask me, Outlook 2007 is a disaster. Why should we all have to disable everything and tweak it to make an EMAIL application work???? Its hardly an SAP or Oracle ERP’s…Its email and contacts…it doesnt need to have so many issues when others manage to get it right…

    Ive done EVERYTHING everyone on many sites have suggested to speed outlook up, and they all work a bit – all by switching functionality off. What I dont understand is HOW people who NEED that functionality get it to work at all!!!!

    Im using outlook for contacts ONLY and its very quick – i tried to manage emails, but I have six accounts for different businesses and different functions and outlook simply could not handle it – crashing more often than not and barely getting through the initial send and receive.

    What I REALLY dont understand is how Outlook 2003 could do it but 2007 cant. Though, i did find out that microsoft (allegedly) butchered the healthy IMAP functionality that 2003 had so it would only work so smoothly with IIS/Exchange to ‘encourage’ businesses to use it (but totally alienating Joe Public)…

    No – if you have more than one email account to manage, forget outlook and look elsewhere. Thunderbird is lightning quick for email – even with six accounts being managed over IMAP…so how can one be lightning quick and the other fall over on its face??? there really is no comparison.

    So, sadly, since Mozilla dont do contacts well at all, and Microsoft do it very well, im using both. Clumsy, but both do the job fast.

    Im totally gutted and infuriated that Microsoft seem to have crippled their own solution for the sake of driving sales of other applications that most of us dont need.


  11. Darren

    August 17, 2008 at 3:57 pm

    Just to add – the tweaks I have found are: Disable the add-ins in the trust center; turn off all the RSS feeds; minimize the number of data files outlook is using (again in the trust center) – if you have only one mail account and upgraded outlook, double check cos it may be using two, when you only need one….if you need more than one mail account, you need one data file for each – delete or archive any surplus ones. You can also try using POP3 instead of IMAP. IMAP is superior, but this is where the politics come in – apparently POP3 should work fine, since its for ‘joe schmo’, but since businesses seem to prefer IMAP, thats where some ‘inhibitions’ were placed to drive business towards IIS/Exchange server….for all of us non-business-heads who want the use of IMAP…I think that answer might be ‘tough luck’ put up with the slowness…

    I am repeatedly and continually shaking my head in disbelief at how Outlook 2007 can be so disastrous in performance with the number of crashes and freezes in ADDITION to slowness and poor IMAP management….

  12. Nate

    September 2, 2008 at 6:26 am

    Wow. So many people with the same group of problems.
    If some of you don’t have multiple large email accounts being handled by outlook then I don’t know why your system is running so sluggish. You may need to look into the system you’re using. Using newer programs means more resources needed to perform the same functions so you may need more RAM or a better processor.

    My Outlook only has problems when initially running after a few hours of being off. I think this person is right about the large .pst files. One of my folders has over 48,000 emails while the others have less than 3,000. The system doesn’t immediately get sluggish, however. It only slows down when it accesses my largest email account.

    I hope this helps. I guess I have to delete a few thousand emails, or is there another fix?

  13. sascha

    November 25, 2008 at 7:24 am

    Running XP with SP3 and all updates applied. system fresh and clean installed two days ago, no spyware,viruses et al. After XP was installed and set up I installed Office 2007 : Word,Powerpoint,OneNote and Outlook – each item installed with all featuresplus the MS DOcument Imaging ( I need Twain/Scanner and the OCR function ) .

    The self built Box is in general speedy enough ( it can even handle Vista well ):

    AMD Athlon x64, ~ 2.2 GhZ, 1GB Ram, 250 GB HDD, Geforce 6200 graphics.

    Right after Office I applied the SP1 for it and installed also the “save as pdf” addin, plus all security fixes and the junkmail updater for outlook 2007.

    I set up one pop mail account and installed the “Connector” to be able to have my hotmail account in Outlook. started using Outlook after all these updates on my snappy and speedy XP Pro – it is unbelievable slow ! Sending two emails with attachements ( both ~ 400-600kb ) over a cablemodem connection took over 20 minutes!

    The *.pst file is under 100 MB.

    This application is broken. A shame I cannot use outlook 03 with the other office 07 apps ( which work quite well )
    SO.. just as a feedback that all these updates do nothing. I think it is defective in general.

  14. MrGroove

    November 25, 2008 at 12:14 pm

    @Sascha – The comment system on blog posts isn’t the best for troubleshooting so I’m going to answer your question in our support forum.

    Please click the link to continue the conversation.


  15. MrGroove

    November 25, 2008 at 12:43 pm

    Comments Closed for this Tutorial.


    Please post all further Questions or Comments in our Free Tech Support Community Forum



  16. Pedro

    June 25, 2011 at 10:50 am

    There’s 5 of us in the office with 4 using win7 and outlook 2007. These 4 are fine. The last one which is win xp pro with sp3 and outlook 2007 is so slow when picking up new mails or sending mails. All tweaking not helping. What I’m considering is remove outlook 7 and install 2003. Will see. Microsoft THANK You.

  17. Dorian Earl

    April 10, 2013 at 3:37 am

    Ok, I think this problem is that over size .pst files, Kernel for split PST software to recover and repair every type of error from ms outlook and split over size pst file split different part for use.

  18. Sytya Sen

    July 3, 2013 at 5:00 am

    Thank you “Dorian Earl” for share wonderful software to me and i am very happy to used this tool to repair my corrupted .pst files and split also over size .pst files. Really Kernel for split pst software is great for me….!

  19. Neelakandan VP

    September 20, 2015 at 11:48 pm

    Hi Guys, Not able to sent the mail with attachment to any user , after changed the IP its working fine . i think IP is blocking that mail , kindly help to resolve this issue

    Without attachment we dont have any problem

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