You may get this error in case you’ve just created a new Outlook account (or an alias) or have not used it for a long time. In such a case, the solution is to log into your account using a normal web browser and try and use your account (i.e. send an email, receive and email etc). Then try logging into 2Do again.
Article ID: 714
Created On: Tue, Dec 15, 2015 at 3:15 AM
Last Updated On: Tue, Dec 15, 2015 at 3:15 AM
Online URL: https://www.2doapp.com/kb/article/i-see-an-error-when-trying-to-login-using-an-outlook-account-account-does-not-have-a-valid-mailbox.html