I changed the default for mail, checking the MAILTO option as well changing it to MS-MAIL (this picture is from my work PC - do not an exact match).
mail.JPG
This did not solve my issue.
I booted into safe mode with networking (damn that's a pain in Windows 😎 and left it that way all night. This morning there were no prompts to pick an Outlook profile.
I'll boot back to normal mode tonight and see if the prompts return.
I looked through the task scheduler and didn't see anything that appeared to either launch Outlook or use the MAILTO option.