When you install Outlook 2010 and try to send mail using the File, Send by email command in other applications, Outlook may not be recognized as the default mail client.

The causes include:
1. You are using Outlook 2010 64-bit and 32-bit programs can't "see" 64-bit programs.
2. You are using Home and Business "Click to Run" (C2R) suite, which is installed in a virtual drive. Other applications can't see Outlook 2010 C2R.

Verify Outlook is set as default mail client

To verify Outlook is indeed set as your default email client:

1. Open Control Panel and search for Default Programs.
2. Select Set Default Programs link.
3. Choose Microsoft Outlook from the list of programs.
   Click "Set this program as default".

Click to Run

If you are using Home and Business C2R, you should uninstall it then log into the download site and download the MSI. This will install the traditional Office suite, which is recognized by other applications.

Use Outlook 2010 64-bit with 32-bit Applications

Using 64-bit Office is not recommended unless you need large (2GB) file support in Excel or Access. There is no benefit in using Office 2010 64 bit version to "normal" users. Also, you cannot mix-and-match Office 'bitness' - you need to use all 64-bit or all 32-bit Office applications. See 64-bit editions of Office 2010 for Microsoft's recommendations.

If you need to use 64-bit Office, you can try the following registry hack.

If you choose to use the following registry hack, you do so at your own risk - it puts Outlook into an unsupported mode. If you have problems with Outlook, you need to remove these keys before troubleshooting. Our recommendation is to use 32-bit Office 2010.

In the Start menu's Search field, type regedit then press Enter. (You'll probably need to ok a security dialog.)

In the Registry editor, browse to
HKEY_LOCAL_MACHINE\SOFTWARE\Clients\Mail
Right click on the Mail key and Export a copy for backup.

Right-click on Mail again and create a new key called Outlook64Bridge

Next, right-click on Outlook64Bridge and create a key under it called DLLPath. Right-click again and create a key called DLLPathEx.

Locate the 32 bit version of the file MAPI32.dll on your computer and enter the complete path name in each DLLPath key (replacing "something\something\...." with the correct path on your computer):

HKEY_LOCAL_MACHINE\SOFTWARE\Clients\Mail\Outlook64Bridge\DLLPath
"C:\WINDOWS\something\something\....\mapi32.dll"

HKEY_LOCAL_MACHINE\SOFTWARE\Clients\Mail\Outlook64Bridge\DLLPathEx
"C:\WINDOWS\something\something\....\mapi32.dll"

(On my computer, a mapi32.dll is at C:\Windows\winsxs\x86_microsoft-windows-mapi_31bf3856ad364e35_6.1.7601.17514_none_ad54ab3a7801c830)

Next, change the default client to Outlook64Bridge:
HKEY_LOCAL_MACHINE\SOFTWARE\Clients\Mail
"Outlook64Bridge"

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Last reviewed on Nov 6, 2011