[Mailman-Users] Non-members keep receiving messages from the listserv

[Hung Phan]

Hello,

We have an odd behavior with non-members keep getting messages from one of
our listserv. We unsubscribe these members manually and receive the message
of "Cannot unsubscribe non-member." We have the 1-click unsubscribe link
embedded to messages as well. When we click on the link, we receive error
message "Authentication failed".

We tried the recipients' names as well and nothing comes back. These
recipients reply to the original message so they are registered as members.

Anybody ran into this issue before? Is there a way for us to force Mailman
to NOT send out messages to these specific addresses?

Thank you,