Windows 10 – Register Mailto Protocol to Custom Program

mailtowindows 10windows-registry

I would like to register my program to handle the mailto protocol.

I have seen these answers

I tried adding a new key or modifying the existing key at this path:
HKEY_CURRENT_USER\Software\Microsoft\Windows\Shell\Associations\URLAssociations\MAILTO\Userchoice.

Additionally, I added my program to to the HKCR root, but that did not make my program appear in the select list.

Also, for testing purposes, I tried changing the classname value of the mailto key at this path:
HKEY_CURRENT_USER\SOFTWARE\Clients\StartMenuInternet\GoogleChrome\Capabilities\
URLAssociations to the classname of my program. This actually worked, but instead of hacking into Google Chrome, I’d rather add my own registry key.

How can I add my program as a legitimate handler for the mailto protocol?

Best Answer

Here is a sample mail client registration - To register with Default Programs / modern Default Apps. You can modify it accordingly, leaving out non-essential parts.

Windows Registry Editor Version 5.00

;RegisteredApplications
;----------------------
[HKEY_LOCAL_MACHINE\SOFTWARE\RegisteredApplications]
"MyMail"="Software\\Clients\\Mail\\MyMail\\Capabilities"


;Clients Key (The path mentioned for MyMail in RegisterdApplications key)
;------------------------------------------------------------------------
[HKEY_LOCAL_MACHINE\SOFTWARE\Clients\Mail\MyMail]
@="MyMail"

[HKEY_LOCAL_MACHINE\SOFTWARE\Clients\Mail\MyMail\Capabilities]
"ApplicationDescription"="Superfast, Light-weight Mail Client for Windows"

[HKEY_LOCAL_MACHINE\SOFTWARE\Clients\Mail\MyMail\Capabilities\FileAssociations]
".eml"="MyMail.eml"
".nws"="MyMail.nws"

[HKEY_LOCAL_MACHINE\SOFTWARE\Clients\Mail\MyMail\Capabilities\StartMenu]
"Mail"="MyMail"

[HKEY_LOCAL_MACHINE\SOFTWARE\Clients\Mail\MyMail\Capabilities\UrlAssociations]
"mailto"="MyMail.mailto"


;Then create handlers for MyMail.eml, MyMail.nws, MyMail.mailto as referenced above

;EML File Type Handler
;---------------------
[HKEY_CLASSES_ROOT\MyMail.eml]
@="MyMail EML Handler"

[HKEY_CLASSES_ROOT\MyMail.eml\shell\open\command]
@="\"C:\\Program Files\\Windows Mail\\WinMail.exe\" -eml \"%1\""


;NWS File Type Handler
;---------------------
[HKEY_CLASSES_ROOT\MyMail.nws]
@="MyMail NEWS Handler"

[HKEY_CLASSES_ROOT\MyMail.nws\shell\open\command]
@="\"C:\\Program Files\\Windows Mail\\WinMail.exe\" -news \"%1\""


;MAILTO Protocol Handler
;---------------------
[HKEY_CLASSES_ROOT\MyMail.mailto]
@="MyMail MAILTO Handler"

[HKEY_CLASSES_ROOT\MyMail.mailto\shell\open\command]
@="\"C:\\Program Files\\Windows Mail\\WinMail.exe\" -mailto \"%1\""

I've uploaded the same in this Pastebin link.

For official documentation, refer Default Programs Registration at MSDN. Although the docs state it's not valid for Windows 10, it certainly applies (and works perfectly) in Windows 10. The registration part hasn't changed a bit in Windows 10.

Also, see: Windows 10 program default settings - Microsoft Community

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