I think RC doesn't offer Share with Email yet? Maybe it needs to be requested as a new feature.
In the meantime you have the option to add an email address in the Admin Portal>Notifications settings for a user. This way all voicemails will be received by the user in the app, and also shared as an email with the email addresses you've added in "Notifications". It's an all or nothing approach, so might be not the right thing for you.
To the same effect you can ask RC Support to enable Shared voicemail. In this way you can select co recipients, which will receive the voicemail in the app(as opposed to via email). Again, your users won't have the choice to share any individual voicemail - all will be shared with the co-recipient if you use this feature.
https://support.ringcentral.com/article-v2/Intro-to-Shared-Voicemail.html?brand=RingCentral&product=MVP&language=en_US
If you want to disable messaging, you need to contact RC Support and tell them you want to remove the Messaging button on the app via the "composability process".
