While creating an email step in a workflow, you can choose if you want to create this step as a follow-up email.
Options | Description |
Send as reply to previous thread | Use if you want to send emails in the same thread as previous email. |
Send as new thread | Use if you want to send email in a fresh thread. This is the default behavior. |
Please note: If you have created 2 email steps in a workflow and the second email step is a follow-up email step, then you can not insert an email step between them.