아래와 같은 에러 로그가 있습니다.
[2008-01-03 00:13:34] "221.141.242.95" "/member.php?mode=LOST_OK" [MAILSEND] "recipients : ****@**** error message : Failed to set sender: @localhost [SMTP: Invalid response code received from server (code: 501, response: Syntax error in return path)]"
[2008-01-03 09:35:47] "203.228.60.198" "/member.php?mode=LOST_OK" [MAILSEND] "recipients : ****@**** error message : Failed to set sender: @localhost [SMTP: Invalid response code received from server (code: 501, response: Syntax error in return path)]"
이런 경우 어떻게 해야 하는지요?