I'm going to use this page as a collection of tips for troubleshooting Microsoft Outlook. Where applicable I'll specify which version of Outlook I'm talking about, otherwise you can assume that any tip applies to all versions equally.
Outlook's default local data stores are PST files. In versions of Outlook prior to Outlook 2003 these files were in a binary format and as those files approached 2 GigaBytes in size they had a nasty tendancy to corrupt. Corruption to PST files can happen at any size, however, and can even manifest in very subtle ways. Outlook 2003 and later uses Unicode PST files which can grow to sizes well beyond 2GB without any corruption issues.
However, just because you're using Outlook 2003 or 2007 (or even 2010) doesn't mean you're automatically off the hook. If you upgraded from an older version of Outlook it's possible that your PST file is still an old binary format file, even though you're using a newer version of Outlook to work with it.
Converting to the New Format
To convert to the new format of PST file click FIle | New | Outlook Data File in Outlook. Step through the dialogs to create a new Outlook data file and make sure to leave the format set to Outlook Data File (rather than Outlook 97-2002 format). As long as you're creating the new file I would place that file in your My Documents folder, just to make it easier to get to. If you're a stickler about keeping your folder tidy then you could create a subfolder of My Documents called "Outlook Files" and locate it in there. (Outlook 2010 is going to do that anyhow)
Once you have your new Outlook PST file created it should appear on your Navigation Pane at the left. Now comes the tedious part - you need to move your old items and folders from your old PST file to your new one.
TIP: To select all of the items in a folder at once select any one item in the folder, then press CTRL+A. Now you can copy or move all of the items in one action to the new folder.
This is a good time, as long as you're moving items and creating folders, to give some thought to your folder structure and what messages you're going to keep. Generally speaking, with the newer versons of Outlook (2007 and 2010) the Windows Desktop Search capability makes it a lot faster and easier to find any item you need. Accordingly there isn't as much need for complicated folder structures anymore. If you need to find a particular e-mail on a particular topic the search tool will locate it for you within moments, even in a folder containing hundreds or thousands of items. Consider flattening your folder structure to make it easier to work with.
Once you're satisfied that you've moved everything you need to the new PST file (did you remember Contacts? Calendar? Tasks? Journal? Sent Items?) you need to go to Tools | Accounts Settings | Data Files (these exact steps will vary a bit by Outlook Version) and make your new PST file the default PST file. Once that's accomplished and you're confident that your e-mail is properly flowing into the new file, you can close the old PST file by right-clicking it in the Navigation Pane and choosing "Close". It won't be deleted, so don't worry if there might be a few stray items left behind. You can always open it again if you need to.
There are a few tools available to help you work with PST files that are misbehaving.
SCANPST.EXE (AKA "Inbox Repair Tool") is a utility provided by Microsoft and automatically installed with Microsoft Outlook.
Running it is fairly easy, you'll find it in the same directory that Microsoft Outlook is installed in - usually C:\Program Files\Microsoft Office. Double click to run it and it will ask you to select the PST file you want to test. Have it run the test. If it finds errors (see picture at right) it will give you the option to back up your data file (which you should) and then click "Repair" to fix it.
When the repair is done, SCANPST will report success. YOU'RE NOT DONE! Now you want to run SCANPST against that file AGAIN. In fact, keep running SCANPST until it gets thru the entire scan and finds NO errors. This could take 2, 3 4 or even more passes to do. If it takes 10...then you may want to just give up and restore from backups.
Once you're done, start Outlook and see if the problem is resolved.
SCANPST's cousin is SCANOST which is used to scan the Offline Data File (OST) of Outlook when used as an Exchange client in cached mode. In most cases SCANOST is totally unnecessary. Why? It's not that OST files don't ever corrupt but rather because the OST file is just a copy of what's in the Exchange mailbox. The only time you need to repair an OST file is if there is data in it that you care about and didn't get to synchronize to your Exchange server.
For most Exchange users the synchronization happens pretty much all the time so it's fairly rare to have unsynchronized data in the OST file. So what do you do about a corrupted OST file? Just rename (or delete it if you're feeling brave) and restart Outlook. Outlook will create a brand new OST file for you and will automatically sync the data from your Exchange mailbox to it.
If you got careless and let an old binary PST file get too close to the 2GB mark you might find that it's too corrupted for SCANPST to do anything with. That's when you need PST2GB.
WARNING: PST2GB is a desperation measure. It WILL TRUNCATE your PST file to get it under the size limit and you WILL lose data. The truncated data is not recoverable.
After you run PST2GB you'll want to run SCANPST against the file as many times as necessary to get a clean scan. Then fire up Outlook and see if you got lucky.
If Outlook is crashing for no obvious reason one thing to try is to start the program in Safe Mode. To do that just press and hold the CTRL key on your keyboard while you click the icon to start Outlook.
If the problem doesn't appear when you're running in Safe Mode then it's probably a misbehaving add-in that's causing the issue. Go to Tools | Trust Center | Add-ins and see if there's anything there you can disable. One that I almost always disable is the iTunes add-in. It's really only useful if you're synchronizing Outlook to your iPhone or iPod.
You can also start in safe mode by using the /safe command line switch. Don't know how to do that? Keep reading...
You can control how Outlook starts, and do some nifty troubleshooting, by using some of the built-in Command Line Switches for Outlook. To use a command line switch just exit Outlook (if it's already running) and then click Start | Run. In the Run dialog box that appears type "Outlook" followed by a space and then the switch you want to use. For example:
Here are a few of the particularly useful command line switches you might want to use:
- /Cleanreminders - If you have pesky calendar issues, especially with ghost reminders, start Outlook with this switch and it will delete all of the reminders from you profile and then recreate them from your items.
- /CleanViews - Resets the Outlook views to the default set that Outlook comes with. CAUTION: any custom views you've created will be lost if you do this and you'll have to recreate them. Still, this is often a way to fix Outlook startup crashes.
- /Resettodobar - Problems with the To Do Bar in Outlook 2007 or 2010? This switch is handy if you're seeing problems like duplicate items or formatting problems with the To Do Bar. It cleans and regenerates the To Do Bar.
- /Resetfoldernames - If you somehow managed to rename one of your default folders you can use this switch to have all of your default folders changed back to their original names. This doesn't affect the content of the folders, just renames them.
- /Resetfolders - If you did more than just rename the folder but actually DELETED one of the default folders...this will recreate any missing default folders at their original location.
- /ResetNavPane - Cleans and regenerates the navigation pane. If you're not seeing what you expect to see in your navigation pane this will reset it and can fix quirky problems with the Nav pane. This can also be the cure for unexpected startup failures in Outlook on occasion.
A lot of modern Antivirus products will scan your e-mail for you as it's received (and sometimes sent too). On the surface of it this seems like a good idea but in practice it often causes problems with Outlook such as blank messages, missing attachments, stalls and hangs and other performance issues. And, it's not even really necessary. If your antivirus software is "running resident" (which means sitting in memory and scanning every file you open/run in real-time) anyhow then any malware that comes into your e-mail won't be able to infect your machine. As soon as you tried to open it your anti-malware software will detect the problem and stop it.
My recommendation is to turn off the e-mail scanning module of your anti-malware software. Outlook will run better without it.
Sometimes problems in Outlook are caused by corruption in your Outlook profile. In those cases it can be a useful experiment to try creating a new profile. To create a new profile go to Control Panel start the Mail applet and click Show Profiles to get the mail applet started. Click "Add" to create a new profile.
If you can't find the Mail applet in Control Panel you may have to click the "View 32-bit Control Panel Items" shortcut. Or you can try to click Start | Run and type MLCFG32.CPL.
Once you've created your new profile change the radio button to "Prompt for a profile to be used" (see pic at right) so Outlook will ask you on startup and you can select your test profile you just created.
Sometimes Outlook crashes can be caused by corrupted views. To test this you can reset the current view by going to View | Current View | Reset View, or you can try starting Outlook with the /cleanviews switch (see above).
First thing to check is if you have your antivirus software scanning your e-mail. See above. If so, turn that off, it can sometimes cause duplicate messages to appear.
Second, how often are you polling for new mail messages? I recommend not polling for new messages more often than every 10 minutes. If you have multiple POP3 accounts and all of your POP3 accounts are from the same server you should split them into at least two Send/Receive groups (Send/Receive | Send/Receive Groups | Define...) and stagger their interval so that they aren't all checking at once.
Next, check your Rules and make sure you don't have a rule that is inadvertently making copies of items in your Inbox. Read each rule carefully, disable any you're not sure you need to have and if you have a rule that is the final word on an item, always end it with "Stop Processing More Rules". That will keep additional rules from firing on that same item, which may cause duplicate items.
Try version 14. Download from Microsoft here.
If Outlook crashes when you try to send messages it's possible that you don't have a correct delivery location specified in your profile. See if the information in this article helps: http://support.microsoft.com/?kbid=2298962
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Troubleshooting Error Messages When You Send/Receive - From Microsoft