In a configuration document for an IBM Lotus Domino server you have the option to configure which IPs are allowed or denied to connect using the SMTP protocol. I would like to share some details on these settings as the field help is not covering all options.
In detail I am refering to the two field "Allow connections only from the following SMTP internet hostnames/IP addresses" and "Deny connections from the following SMTP internet hostnames/IP addresses".
Your first option is to use full qualified hostnames or parts of that. As an example ".brandlehner.at" will match all hosts in that domain like "mail.brandlehner.at" but will not match "mail.anotherbrandlehner.at".
The second option is to use IP addresses in square brackets: "[18.104.22.168],[22.214.171.124],[126.96.36.199]"
You can use a dash to define a range of IP addresses: "[188.8.131.52-3]" or you can use a wildcard: "[1.2.3.*]" which will match all hosts in that network.
The third option is to use CIDR notation
Some valid examples:
- .brandlehner.at, [127.0.0.1], [192.168.1.0/24]
- .brandlehner.at, 127.0.0.1