Receiving bounce when sending email to configured default Jira Core mail handler

Summary

User is receiving bounce emails when sending email to Jira Core configured default mail handler, for example:

This message could not be delivered.
Action: failed
Final-Recipient: rfc822; jira@test123.atlassian.net
Original-Recipient: rfc822; jira@test123.atlassian.net
Diagnostic-Code: smtp; 550 5.1.1 Mailbox does not exist
Status: 5.1.1

This happens in case there are more than 1 Mail Server configured in Jira Core ('Incoming email' section) that has 'host' specified as 'mailstore':

Expected Results

Email is received by Jira and processed successfully

Actual Results

Bounce is received 3 hours after email is sent

Workaround

This situation may happen in case there are Mail Servers configured from Jira Service Desk, name of such Mail Server is automatically generated and will be like:

Mail server for <project_name>@<instance_name>.atlassian.net. Created by JIRA Service Desk.

 Make sure there are no Mail Handlers configured for this mail server. If so, remove such Jira Service Desk Mail Server.