Can the list be moved to a server that supports IPv6 transport? E.g., it looks like all the ops.ietf.org lists are delivered over IPv6 now.
I have received messages for the multi6@ops.ietf.org list over IPv6 once in a blue moon, but it's IPv4 99% of the time. Also:
> host -t mx ops.ietf.org ops.ietf.org mail is handled (pri=0) by psg.com > telnet -6 psg.com 25 Trying 2001:418:1::62... telnet: connect to address 2001:418:1::62: Operation timed out telnet: Unable to connect to remote host