The error message "The connection does not have a valid email associated" means that you are trying to log in with a Microsoft account where the associated email is not eligible for sending email from Microsoft/Outlook 365 servers.

Some Microsoft accounts do not have a working email address associated, and if you try to connect such an account, we would not be able to send emails on your behalf using that. That's why you see that error message.

The email associated with the account should be an Outlook/Office 365-enabled email. To examine if the email is eligible for sending and receiving, you should be able to log into https://outlook.office.com/mail/ and send and receive email there.

You may still be able to use such a Microsoft account to log into Myphoner. But you can't use it for sending emails on your behalf.