You can disable the User Activation Email notification under Admin--> General Settings→ Email Notifications to sign up for Freshservice. However, there is no email notification present for the ''User invitation'' email which gets auto-generated from the backend. Read below to understand the difference between User Activation Email and User Invitation Email.
User Activation Email: This email is sent to users when they sign up for Freshservice or any other product under the Freshworks organization for the first time. These users are new to the Freshworks and do not have an existing account with any other Freshworks product.
You can edit this email from the Email Notifications. It can also be enabled or disabled as needed.
User Invitation Email: This email is sent to users who sign up for Freshservice but already have an existing account with another Freshworks product (such as Freshdesk, Freshchat, Freshsales, etc.).
To disable this email, please contact us at support@freshservice.com