Using Techtool Protection, you can get email notifications if SMART is failing or a drive becomes too full. If the email address you're using for email authentication is an iCloud address, and two-factor authentication is enabled, you'll need to perform an extra step to get it working. 

First, you'll want to log into your Apple ID account at and access your iCloud settings. (If you have to get a message on your phone or iPad before logging in, this confirms that two-factor authenticaion is enabled.) Click Edit for Security Settings, and then click on Generate App Specific Password. Create a password, and name it something that will remind you that it's for Techtool Protection. Copy that password and paste it into the Password field in Techtool Protection's email alerts password field. This should allow email alerts to send emails, provided the remaining settings are correct.