Hi, Which email client are you referring to? Are you facing issues opening any e-mails? I would recommend you to perform clean boot.
Configuring your system in clean boot state helps in identifying if any third party applications or startup items are causing the issue. If yes, you may have to contact the program manufacturer for any updates or uninstall and re-install the program.
Refer the following Microsoft KB article for more information on how to troubleshoot a problem by performing a clean boot in Windows Vista or in Windows 7:
How to troubleshoot a problem by performing a clean boot in Windows Vista or in Windows 7 http://support.microsoft.com/kb/929135
Note: After troubleshooting, make sure to put the computer to start as usual as mentioned in Step 7 in the above KB article. Reply back with more information. Also refer: http://support.microsoft.com/kb/555375
Go to the Start button.
In the Search box, type "regedit" (without quotes) and press Enter.
Look for the following registry key: "HKEY_LOCAL_MACHINE\SOFTWARE\ Microsoft\ SQMClient\Windows\DisabledSessions".
On the right window pane, delete the subkey: "Machine Throttling".
Reboot your system.
Recommended Method to Fix the Problem: can't open certain e-mails error message c00d1199:
How to Fix can't open certain e-mails error message c00d1199 with SmartPCFixer?
1. Download SmartPCFixer. Install it on your computer.
2. After the scan is done, you can see the errors and problems need to be fixed. Click Fix All.
3. The Repair part is done, the speed of your computer will be much higher than before and the errors have been removed. You can also use other functions in SmartPCFixer. Like dll downloading, junk file cleaning and print spooler error repair.