Email Security Issues

Hello, I have my own dedicated servers, I have only corporate hosting accounts hosted. I am facing issues these days. I want help. 1. Cpanel has suspend incoming option in email accounts option but there is no option for suspend outgoing feature. I have searched people has requested this feature and it is also added in current version maybe if i am not wrong. But my settings are set to released I am still waiting for this feature. It is very important for me. I have a company who has many email accounts for staff but basically head office uses emails to send emails to outside and local notifications to staff.. I want to suspend staff emails outgoing and keep active incoming that will save spamming please.. 2. If this feature is not yet release how i do it through any methods. 3. Company want default webmail as roundcube. e.g. when they open webmail.domain.com they want direct roundcube webmail no any other. So i am thinking i install roundcube through softaculous and create sub domain for them is it fine and secure way? I also want to add restriction on that roundcube installation through htaccess so it will only open in local country. Please guide me which is better way for them. Because if in cpanel webmail they give staff. There is option for password change etc they dont want to give this option to staff..