Hi,
try executing this command:
# /usr/local/psa/admin/sbin/mailmng-domain --unset-reject --domain-name example.com
Then check what the Panels says.
If Catchall is disabled, try:
# /usr/local/psa/admin/sbin/mailmng-domain --set-catchall --domain-name example.com --email
[email protected]...