log 里一大堆：
"recipient-domain": "stu.xjtu.edu.cn",
"event": "failed",
Requested action not taken:app1, MwGowACnRdlcHb5kmrHIAA--.42662S3, dnsbl.sorbs.net, please try again
Requested action not taken:app2, NAGowAAX6iNIHr5kEUrOAA--.11485S3, dnsbl.sorbs.net, please try again
Requested action not taken: MwGowABnKdY7Bb5kd4DIAA--.30067S3, please try again
Requested action not taken: NAGowACXSSo7Bb5kChfOAA--.53191S3, please try again
Requested action not taken: MwGowAA3+tap671kTUrIAA--.9346S3, please try again
