症状

• When we receive an email from Jira, the outgoing email address is used instead of the project specified emails address in the received emails.
• This applies to both Jira and Jira Service Management.

診断

Gmail is being used as the outgoing mail server. 

原因

This is a restriction of Gmail. 

ソリューション

Since this is a restriction in Gmail, please follow the steps as described in Send mail from a different address or alias.