As per the docs, users with write access to the current table can see the email icon. To remove the icon, remove the user's write access to the table.
Typically you do this in one of two ways:
- Make the user an Employee Self-Service (ESS) user. ESS users do not have a user role, and without a role they do not have write access to the Incident table. Making a user an ESS users, therefore, hides the email icon on the Incident form.
- Create a custom ACL rule and user role that does not have write access to the table. The default ACL rule for the email client checks to see if the user has the itil role. If you grant users a custom role other than itil, then any such users will not see the email icon.
The ACL that controls the email is the following:
If you add the desired role into this, the user will be able to see the email button.