On a computer that has Microsoft Office Outlook 2007 installed, when you try to open an Outlook Message Format (.msg) e-mail message file that contains many attachments or many recipients, you may experience one of the following symptoms:
When you double-click the .msg file to open the message in Outlook 2007, the message does not open. Additionally, you receive the following error message:
The operation failed due to a registry or installation problem. Restart Outlook and try again. If the problem persists, please reinstall.
When you use a MAPI-based application such as MFCMapi.exe to view the properties of an .msg file, the message does not open. Additionally, you receive the following error message:
To resolve this issue, follow these steps.
Important This section, method, or task contains steps that tell you how to modify the registry. However, serious problems might occur if you modify the registry incorrectly. Therefore, make sure that you follow these steps carefully. For added protection, back up the registry before you modify it. Then, you can restore the registry if a problem occurs. For more information about how to back up and restore the registry, click the following article number to view the article in the Microsoft Knowledge Base:
322756 How to back up and restore the registry in Windows
Apply hotfix 951995. For more information, click the following article number to view the article in the Microsoft Knowledge Base:
951995 Description of the Outlook 2007 hotfix package: April 28, 2008
Add the AttachmentMax registry entry and the RecipientMax registry entry. To do this, follow these steps.
Note The default value for the AttachmentMax registry entry is 2048 attachments. The default value for the RecipientMax registry entry is 2048 recipients. If you set these registry entries to larger values, it can cause long delays when you try to open .msg files that have lots of recipients or attachments. This is expected and is the reason the original limit was established.
Exit Outlook 2007.
Start Registry Editor.
In Windows Vista, click Start, type regedit in the Start Search box, and then press ENTER. If you are prompted for an administrator password or confirmation, type the password or provide confirmation.
In Windows XP, click Start, click Run, type regedit in the Open box, and then click OK.
If you do not use policies, locate and then click the following registry subkey: