One of my users wants to set an alert for an external user. To receive the alert the external user must be listed as a guest user in our Office 365 portal and therefore they need to login the first time.
But the problem is, that the user only receives a verification code, he doesn't get the option to create or login with a Microsoft account.
Now I tested it with a new Gmail account, I indeed receive a verification code an not an option to create an account. After user the verification code the guest user isn't created in our tenant.
So I created a Microsoft account with the new Gmail account, invited the test user again thinking I know would get the option to login with my newly created Microsoft account, but nope, a verification code again.
If you send an Anyone link, then the recipient will never need to sign-in (and thus no account will be created).
If you send a specific people link, that is also the case today (there are some cases when the recipient is using O365 and they do get an account in your directory). If you enable the new preview though, you'll find that all guests do get an account created. Hope that helps!