Sending an email in a project automatically moves it to the follup stage

Sending an email in a project automatically moves it to the follow up stage. (this is not an automation I created, it is a built in automation). How do I turn it off?   Once I set it to planning, I want it to stay there even if I send the client an email.  Once the contract is signed and deposit is paid, I want it to be stage planning and stay there until complete.  I used tags and tasks for details within the planning process.