Gmail rejecting Flute List Listserv Digests
Last error: 5.7.1 @gmail.com; 550-5.7.1 [91.136.10.194 12] Our
system has detected that this message
Looking this up, it’s likely 550, "5.7.1", Our system has detected that this message is likely unsolicited mail. To reduce the amount of spam sent to Gmail, this message has been blocked. For more information, visit
https://support.google.com/mail/answer/188131