If I'm switching to
email@example.com emails and using a third-party email service provider that I trust (for example, Google Apps), what potential security threats do I need to secure my system against?
Note that I am not referring to security threats pertaining to the email provider here (e.g. so I'm not talking about my Google Account's password or 2-factor authentication here).
Rather, I'm talking about the parts of the system that come before that.
For example, one thing I can think of is locking my domain name so it can't be transferred (ClientTransferProhibited), although that's pretty general, and not specifically email related.
What else do I need to guard against?