It looks like your system has general IPv6 support, but not every interface has an address.
root@84ef201c4887:~# /usr/sbin/amavisd debug ... Apr 16 06:59:31.912 mail.example.com /usr/sbin/amavisd[107]: Net::Server: Binding to TCP port 10024 on host :: with IPv6 Apr 16 06:59:31.912 mail.example.com /usr/sbin/amavisd[107]: (!)Net::Server: 2025/04/16-06:59:31 Can't connect to TCP port 10024 on :: [Invalid argument]\n at line 66 in file /usr/share/perl5/Net/Server/Proto/TCP.pm Apr 16 06:59:31.912 mail.example.com /usr/sbin/amavisd[107]: sd_notify (no socket): STOPPING=1\nSTATUS=Server rundown, notifying child processes.
root@84ef201c4887:~# grep . /proc/sys/net/ipv6/conf/*/disable_ipv6 /proc/sys/net/ipv6/conf/all/disable_ipv6:0 /proc/sys/net/ipv6/conf/default/disable_ipv6:0 /proc/sys/net/ipv6/conf/eth0/disable_ipv6:1 /proc/sys/net/ipv6/conf/lo/disable_ipv6:0
root@84ef201c4887:~# echo 0 > /proc/sys/net/ipv6/conf/eth0/disable_ipv6
root@84ef201c4887:~# /usr/sbin/amavisd debug ... Apr 16 07:01:17.112 mail.example.com /usr/sbin/amavisd[122]: Net::Server: Beginning prefork (2 processes) Apr 16 07:01:17.112 mail.example.com /usr/sbin/amavisd[122]: sd_notify (no socket): STATUS=Starting child process(es), ready for work.
