For some reason JIRA has created two user accounts on my JIRA OnDemand instance called "MAILER-DAEMON@emx1.uc-1.atlassian.com" and "MAILER-DAEMON@emx2.uc-1.atlassian.com". I don't know why these users were created or what they are for, if these user accounts are not needed would it be safe to remove them?