MAILTO keeps defaulting to Outlook Classic

Question

Hello good people.

I have switched to New Outlook (for better or worse), but I have an issue with the MAILTO and Default apps association. Via settings I'm assigning the MAILTO link to default to New Outlook, but after a restert the association reverts back to Classic Outlook.

This causes an issue when I click any email URL, and I have to re-associate the MAILTO link every time.

Is this a known issue?

Answer 1

I'm not OP but I am having the same issue.

HKEY_CLASSES_ROOT\mailto\shell\open\command

has the following value: "C:\Program Files\WindowsApps\Microsoft.OutlookForWindows_1.2025.506.300_x64__8wekyb3d8bbwe\olk.exe"

and after a restart it still has the same value, however when I go to the defaults in windows settings it is showing the legacy outlook as the default for mailto and when testing a mailto link it opens a new email in legacy outlook until I change the default in the settings UI.

I use mailto links to automate templates for work and the old outlook does not include my signature when using a mailto link with a body nor does it send my emails until I open a instance of legacy outlook for it to notice the emails in my outbox.

Any suggestions?

Answer 2

Michael

I have since found that my original info was out of date.

https://techcommunity.microsoft.com/blog/outlookglobalcustomerservice/set-outlook-as-default-mailto-application/1454942

• Before Windows 8, you could control the handling of the MailTo protocol by deploying a single registry value or group policy, thus setting outlook.exe to Default:
• HKEY_CLASSES_ROOT\mailto\shell\open\command
• However, the above method does not work in Windows 8 and Windows 10. The default application for the MailTo protocol is now stored here:
• HKEY_CURRENT_USER\Software\Microsoft\Windows\Shell\Associations\URLAssociations\MAILTO\UserChoice

And it's a Hash value, not a simple string you can edit.

As to your problems of getting Classic Outlook to respond correctly to execution from a mailto link, I am sorry, but I don't have any suggestions. You will probably need to Contact Microsoft Support. https://support.microsoft.com/contactus

Answer 3

Do I understand correctly

• You have (in essence) followed instructions similar to these: https://servicedesk.shu.edu/space/PUBLICKBA/3006758914/Set+or+Reset+Default+Email+App+for+%22mailto:%22+Links
• And it works (opens New Outlook) when you invoke a MAILTO link.
• But when you reboot it reverts back to the previous default app (Classic Outlook)

If you examine the Registry key

HKEY_CLASSES_ROOT\mailto\shell\open\command

What program is the {Default} value pointing to?