You may set up your account so it automatically starts mail the moment a lead is added.
This option can be useful for team owners who do not want to review and approve each lead submitted by their team. To set this up,
Click your profile picture (or your initials if you don't have a picture yet) at the top right corner of your screen.
Scroll down and click Application Settings.
Click Basic Automation.
Scroll down and toggle on "Start mail when lead is added".
With the option enabled, the system will automatically start the default design or mail sequence for a lead when it is added. How do I set my default template/mail sequence?