[Mailman-Users] Server request addresses not active

Hello list,

I'm new to mailman and have recently installed the software on my CenOS server.

All is working quite well, accept for the specified join & leave dedicated addresses for members to subscribe/unsubscribe.

When sending to ios-join@a11y.us, the message is rejected, as a "mailbox doesn't exist" type of error. Same goes for ios-subscribe@a11y.us.

Any ideas on what I should explain to my I.T rep to review, so these requests can work?

Thank you.

Carlos