Each time an email is to be sent, the default email opens as Outlook Express, where an alternate application is desired. As in this case, where Yahoo! Mail is the desirable email client. Microsoft Internet Explorer offers no alternative or customization. Yahoo apparently offers the available option through Yahoo Messenger through a custom install with the Yahoo! Browser Services selected. However, attempting this with the latest version 9.0, that option does not exist. Another alternative offered by Yahoo! is to install the Yahoo! Toolbar, which is undesirable and just something else to clutter up the internet interface of Internet Explorer. Then there is another option, that after considerable research, I have found and have used with success, a registry entry with a single Yahoo dll.

The Patch

• Download a Yahoo! DLL called yammapi.dll
• Copy yammapi.dll to C:\Program Files\Yahoo!\Common
• Apply the registry patch listed below. (source)

Windows Registry Editor Version 5.00

[HKEY_LOCAL_MACHINE\SOFTWARE\Clients\Mail\Yahoo! Mail]
@="Yahoo! Mail"
"DLLPath"="C:\\PROGRA~1\\Yahoo!\\Common\\YMMAPI.dll"
"LocalizedString"="Yahoo! Mail"

[HKEY_LOCAL_MACHINE\SOFTWARE\Clients\Mail\Yahoo! Mail\DefaultIcon]
@="C:\\PROGRA~1\\Yahoo!\\Common\\YMMAPI.dll,-201"

[HKEY_LOCAL_MACHINE\SOFTWARE\Clients\Mail\Yahoo! Mail\InstallInfo]

[HKEY_LOCAL_MACHINE\SOFTWARE\Clients\Mail\Yahoo! Mail\Protocols]

[HKEY_LOCAL_MACHINE\SOFTWARE\Clients\Mail\Yahoo! Mail\Protocols\mailto]
@="<a href="MailTo">URL:MailTo</a> Protocol"
"EditFlags"=hex:02,00,00,00
"URL Protocol"=""

[HKEY_LOCAL_MACHINE\SOFTWARE\Clients\Mail\Yahoo!
Mail\Protocols\mailto\DefaultIcon]
@="C:\\PROGRA~1\\Yahoo!\\Common\\YMMAPI.dll,-201"

[HKEY_LOCAL_MACHINE\SOFTWARE\Clients\Mail\Yahoo!
Mail\Protocols\mailto\shell]

[HKEY_LOCAL_MACHINE\SOFTWARE\Clients\Mail\Yahoo!
Mail\Protocols\mailto\shell\open]

[HKEY_LOCAL_MACHINE\SOFTWARE\Clients\Mail\Yahoo!
Mail\Protocols\mailto\shell\open\command]
@="rundll32.exe
\"C:\\PROGRA~1\\Yahoo!\\Common\\YMMAPI.dll\",MailToProtocolHandler %1"

[HKEY_LOCAL_MACHINE\SOFTWARE\Clients\Mail\Yahoo! Mail\shell]

[HKEY_LOCAL_MACHINE\SOFTWARE\Clients\Mail\Yahoo! Mail\shell\open]

[HKEY_LOCAL_MACHINE\SOFTWARE\Clients\Mail\Yahoo!
Mail\shell\open\command]
@="rundll32.exe
\"C:\\PROGRA~1\\Yahoo!\\Common\\YMMAPI.dll\",OpenInboxHandler"

Change the default email program

• Open Internet Explorer > Tools > Internet Options to open the Internet Properties window
• Click the Programs tab along the top
• Click the E-mail pull-down menu, and select Yahoo! Mail.
• Click OK.
• Done!