[Mailman-Users] Recipient address rejected

[c cc]

Hi,

We have about 30 mailing lists on our Mailman using Postfix and all
the lists and emails are working fine, except one list. In this
particular list, we receive the following message below whenever we
try to send a message to the list.
We could subscribe and receive subscription confirmation, but only
when we try to send a message to the list. Does anyone know have any
idea what the problem is? Thanks!
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An error occurred while sending mail. The mail server responded:
5.1.1 <list123 at example.com>: Recipient address rejected: User unknown
in local recipient table. Please check the message recipient
list123 at example.com and try again.