Improve the security control for custom email notification sender

Problem Definition

To change the default email notification send on Jira (see this doc) it is needed that the user verify the domain using DNS method and add an SPF and DKIM records to the DNS table.

The issue with this current option is that, after the domain is verified on Atlassian, any cloud instance could use that domain to send messages (as long as they use the correct email address).

Suggested Solutions

Create a mechanism to allow users to select the cloud sites that are authorized to use the custom email domain.