How to register custom program to handle mailto protocol on Windows 7

Question

OK, it might be a problem with my system but I'm having a very difficult time getting Windows 7 to recognize my custom exe as the default handler of the mailto protocol.

First, I've seen this: Register Windows program with the mailto protocol programmatically

Next, I've seen these:

• How to Register an Internet Browser or Email Client With the Windows Start Menu
• Registering an Application to a URL Protocol

I've added what seemed the appropriate registry entries but I still get Windows Live Mail coming up every time I click a mailto link (whether in a browser or via the Run window). I've set the registry entries for all users and for the current user, still it doesn't work.

When I go to the 'default programs' app and scroll down to the mailto protocol, I only see Outlook and Windows Live Mail listed. My custom app doesn't even appear.

I figure that it's either something special with Windows 7 or it's something with my computer.

My custom app is a WinForms .Net app but I don't think that matters.

Any ideas are greatly welcome.

Answer 1

The way described in the answer which you referenced in your question seems correct way for Windows 7 as for other operation systems.

I suppose that you use 64-bit version of Windows 7 and your program is 32-bit application. So if your application write in the HKEY_LOCAL_MACHINE\SOFTWARE\Classes\mailto\shell\open\command key it modifies only the key HKEY_LOCAL_MACHINE\SOFTWARE\Wow6432Node\Classes\mailto\shell\open\command used for 32-bit applications. You can read more about registry virtualisation here and here.

If it's your case you can call directly native Win32 API RegOpenKeyEx with the KEY_WOW64_64KEY flag which will be ignored on 32-bit operation system.

Answer 2

Though a pretty late answer, what worked out for me is this: On regedit, this supersedes the registry keys mentioned in other answers:

HKEY_CURRENT_USER\Software\Microsoft\Windows\Shell\Associations\URLAssociations\MAILTO\Userchoice

Have a look at this page: Default Mailto Registry

Answer 3

How can I add a custom url handler on Windows. Like iTunes itms:// Related but not.

Answer 4

This seems like a very high-nerd-level context to a fairly common problem. As a nerd, I'm swept up by the discourse on 64 vs x86 and the pseudo-universal binary aspects of .net. But the tech support troubleshooter in me can't help but think that the core problem needs to be made plain and addressed systematically...

So your real problem, regardless of the mail client (as you said yourself), and regardless of your CPU, is that you can't get your mail client to be the default protocol handler for mailto. Or to make it really simple, you can't get the program you like to be the default program.

I'm inclined to think that the 64/86 aspects of the problem are not relevant. They are interesting, and possibly having some effect, but if the program is running just fine (no issues with the code in that architecture, etc), and if it does email just fine (emails get send and received, all SMTP and IMAP all the way), then I doubt the OS is plotting to keep the client from taking over as the leader of the porch dogs.

If anything, I would say that the client had self-esteem issues and is afraid to be the mailto protocol handler. Most clients can't resist asking if the should be the primary and if you say yes, they pass the word along to the other apps and to the registry. They make sure everyone knows they are the new Mailbox king in the house.

So, what I would try first (basic troubleshooting): install another mail client and see if it has the same issue. If it does, your OS is a bully and you'll want to explore such routes.

But if this other client can get into the default programs club and be made the mailto handler, then the problem is with your app. It's a big wimp that doesn't know how to properly assert himself.

But like so many underdogs waiting for a cool kid to take them under their wing (and by wing, I mean Thunderbird. Don't bother with any other client), your app can stand on the shoulders of the working third-party client.

We have to assume that Thunderbird did at least one and possibly two things that your app didn't do. The first was getting it's name tied to the protocol in the registry. Go poke around and see if you can find his name and how it's associated to the mailto protocol. Chances are good that you can swap out his name for yours, or at the very least try to pin the protocol to you as well.

The second thing that T-Bird may have done was get himself in the "Default Programs" list (a feature of 7 that I didn't really like, because it had a cool concept behind it -- ie, let's group apps together up front rather than wait and see every time if one of them can do a similar job. But Windows screwed that good time (big surprise) by acting like the overprotective parent it always is, and showing up at the kids' party and saying "I think these two should be in this group, don't you?"

Well, my hope is that by getting access to the mailto by borrowing it from Thunderbird, that you'll be welcomed into the default programs club, but if you aren't and you are still the mailto handler, I'd write it off, at least gloat about it for a week or two, before trying to tackle that issue.

Now, if Thunderbird can't get mailto control, I'm very inclined to think that Windows 7 as actually put in to place some sort of strange caste system, where the application and it's installer (eg user) must some how prove their worthiness to be in the group by figuring out what the big secret is.

Oh, and if all else fails, try restarting in Safe Mode with no networking, install your client in that environment, and starting it up. See if you can't make it the default while the others are in suspended animation. Do a test run (with no network, obviously) by writing a basic HTML page with a mailto and see if clicking on it opens your client.

THen cross your fingers when you start back up in normal mode.

Let me know if any of the above proved the least bit helpful.