지메일로 메일발송시 아래와 같이 리턴. 550-5.7.1 [x.x.x.x] This message is not RFC 5322 compliant, the issue 550-5.7.1 is: duplicate To headers. To reduce the amount of spam sent to Gmail, 550-5.7.1 this message has been blocked. Please review 550 5.7.1 RFC 5322 specifications for more information. u189-20020a6279c6000000b0057629288720si12847103pfc.176 - gsmtp (Tried: Tue,06 Dec 2022 10:40:11 +0900) 헤더를 분석해보니 아래..