1. When an email invalid is logged, the reason is logged but not the email address that failed the check.
2. In the case of authentication, the username is checked to be a valid email address. In such case, it is expected that it may be invalid. Hence, we may want to add a valid to control whether invalid email log should show up or not.

The current behavior shows confusing entries in EventLog plugin like:

1613 2016-09-06 07:29 UTC [MAIL] failed - invalid address