When adding Outlook as your email provider, sometimes authorization will fail with the following error:

535 5.0.0 Authentication Failed 

The error message indicates that Microsoft has blocked our servers from accessing your email address. If you log in to your Outlook account, you should have received an email from Microsoft with the title: 'Microsoft account unusual sign-in activity'. This will happen to any email client that uses SMTP or IMAP to connect to Microsoft servers.

To allow access to Event Temple, follow the steps in the email you received from Microsoft to whitelist Event Temple.

Once you are done, go back to your email setting inside Event Temple and authorize again.