https://confluence.atlassian.com/display/AOD/Creating+Issues+and+Comments+from+Email
I tried the following methods to add a comment to an existing issue from the mail in reference to the above site.
JIRA Ver:5.2.2
Mail Client:OutLook365
Issue key: ABC-25
Email subject |Result
-----------------------------------------------------------
ABC-25あいうえお | Challenge is newly created.
あいうえおABC-25 | Challenge is newly created.
ABC-25 | Comments are added to an existing issue.
Question
Please tell me how to add a comment by applying the issue key in the subject line of the email.