"create a new issue or add a comment to an existing issue" mail handler not working

Summary

Replies or forwards via email are getting into JIRA as comments of the original email instead of new tickets even though there is no issue-key on the subject.

Environment

• JIRA v1000.610.2

Steps to Reproduce

1. Have a "Create a new issue or add comment to an exiting issue" mail handler set
2. Send an email to that mail handler
   • JIRA will create a new ticket (e.g.: AB-1)
3. Reply or forward that same email to the mail handler

Expected Results

JIRA should create a new ticket since there's no issue-key on the subject of the email

Actual Results

JIRA is adding a comment to the first ticket it created (AB-1)

Notes

Our Creating issues and comments from email documentation states that:

This handler creates a new issue or adds a comment to an existing issue. If the subject contains an issue key, the message is added as a comment to that issue. If no issue key is found, a new issue is created in the default project.

Workaround

If a new ticket needs to be created, do not use forward or reply. Copy the email content and send a new one.