Hello and welcome to the forums,
I understand you want your regular users to have "E-mail" option available under "Menu", is that correct?
By default, every Employee has access to E-mail client integrated in EPESI. To have your users access this (and many, many other features) make sure you created a contact for every one of them and that these contacts are assigned to the Main Company.
Main Company is usually the first company, the one created during the installation.
To assign a contact to the user, create (or edit) a contact and in the tab "Login Panel", select user login from the dropdown.
Kind regards,
Arek