Since a few days, the mailing list manager for l4-hackers only accepts messages sent by list members. This policy has been implemented to reduce the amount of spam.
Until a few minutes ago, messages sent by non-members disappeared into a black hole. I just got bitten by this myself because my subscription address used to be different from my sender address. We have changed this now so that illegitimate senders get a bounce message.
I will re-send a few of my messages which vanished into the black hole later today.
Michael