There are some user profiles from whom we have only a phone number, means we have not recorded any email address in their user profile's contacts section. In many cases, the agent can still create a public message within the ticket and if they don't check the user profile, they will think that they have updated the ticket via email and the ticket will be pending for customer reply, even though the customer has never received any email.

I couldn't find any native solution from zendesk to get an error message or something to inform the agent that they cannot send an email to that user. so I tried to create triggers & views to filter tickets that were updated via email without having an email address in user profile. But I couldn't identify such a tickets properly, as I couldn't find any way through triggers to find out which user profile has email address recorded or not. The only way for me so far, is filtering via the channel that ticket is created/updated or if the update has been via email or not, which cannot target the right tickets and there are always many tickets selected incorrectly and still manual monitoring is needed.