To disable IPv6 on the postfix mail server, edit
vi /etc/postfix/main.cf
Find
inet_protocols = all
Replace with
inet_protocols = ipv4
Restart postfix
systemctl restart postfix
Method 2
postconf -e inet_protocols=ipv4 systemctl restart postfix
To see the current configuration, run
[root@server ~]# postconf inet_protocols inet_protocols = ipv4 [root@server ~]#
