- Case 1: When user creates an account, a confirmation email is sent.
- Case 2: When user invites a coworker to his/her account, an invitation email is sent.
Problem: If a user makes a typo in the email, it cannot be delivered.
It might be more user-friendly to immediately show an error message to a user if this email cannot be delivered. So this user won't waste time waiting for this email and could fix the typo. The potential risk is that someone can use it to check for someone's else mailbox existence. But there are easier ways to check for email address existence, and with throttling, the risk can probably be mitigated.
I wonder if I missed something from the security point of view.