Notify users when trying to email to a user without email address

• Feature Request Summary

When a user has no email address set it's still possible to send a public comment. That message is going nowhere.

• Use Case

A user can be added to your Zendesk environment without setting an email address. For example when you create a user manually or when a user is created automatically when they call you. While the user has no email, it's still possible to send a public message to this user. You have the feeling that you're message is going somewhere, but it ends up nowhere.

• Product limitation or missing feature

Notify the current agent or make it impossible to send public messages when you only have email as messaging option installed.

• Business impact of limitation or missing feature

Agents assuming they're contacting customers, customers without responses. I have no figures, as these cases are pretty hard to spot.