How can a Case manager/Case worker send email to non-case worker employees through conversation?

Summary: We want to allow the case managers/workers to send messages through email to employees who are non-case workers (Do not have Case Worker or Case Manager role). We are implementing Case management under Help Desk module.

Content (please ensure you mask any confidential information): We have a requirement to send messages via email to employees who are not a case worker or case manager from Case > Conversations page. Currently, under the Conversations section when I select Create Conversation > select Channel Type as Email, in the To field I can only search the case workers/managers (All Resources). I want that when I type a person's name in the