What is a good flexible way to send auto system emails to users? I would like to know a good user friendly, easy to setup and flexible way to send automated emails to users. This will be in response to an event triggered by a user. I guess it does not matter what it is for. Just need a good way to send system emails, which is widely used.
I think the most easy and user friendly way for you is to use Rules module.

EXAMPLE:
Create new rule

Add action




Follow next steps to set your mail.