Accepted IP’s and general information pack:

Source networks (IPv6):

2c0f:fc00:a000:1510::/64

2001:a68:e:10::/64

2001:1bc8:201:fd10::/64

Source networks (IPv4):

196.36.18.0/26

81.17.201.0/26

188.117.33.64/26

Or source networks:

net 196.36.18.0 netmask 255.255.255.192
net 81.17.201.0 netmask 255.255.255.192
net 188.117.33.64 netmask 255.255.255.192

Notes:

1. Do not leave any other IP’s since they may cause a by-pass route to the email server.

2. In some cases the target email server needs to be configured accordingly.

Source = Source address from the Internet
Destination = Destination address (client-owned)
Protocol = TCP/UDP/ICMP/IP
Service = exact/ANY (preferably a port number)
Action = function (usually accept)