Handle users who reply via email from a different address

Even at our fairly small company, it's surprisingly common for a user to sign up with their company email and use that to create cases in our Jira Service Desk web screens. Then at some point down the line their email address changes or they have multiple emails pointing to the same inbox.

Then, when we add a comment and they are notified, the notification goes to their original email (which they get), but when they respond, their email client sends the response using their new email address. When this happens Jira Service Desk create a new separate case.

It's difficult for us to track all the cases and comments and it's difficult for our customer to understand that they now have multiple Service Desk accounts and their issues are spread across the two.

What can be done about this? My thought is in a Service Desk account, allow us to specify alternate alias emails for that user. They wouldn't be used to send anything out, but would be allowed for incoming messages so they don't create a new issue each time they comment.