Before you start
Things you need to know:
You must create a separate transactional email user to send using SMTP. This is different from an API user.
Create a transactional email user for SMTP
Expand the User menu, then go to Settings > Transactional email > Credentials.
Select NEW USER.
Enter a Description, Password, and Status.
Select SAVE.
These are your credentials for sending transactional emails using SMTP.