I added an IP-address and domain to Postfix Whitelist in E-Mail -tab. From reading https://www.howtoforge.com/how-to-whitelist-hosts-ip-addresses-in-postfix How To Whitelist Hosts/IP Addresses In Postfix, I assumed ISPConfig would modify /etc/postfix/main.cf. But I see no changes to any files in /etc/postfix. Did the whitelisting really do something? How could I verify the whitelisting works? I used the whitelist because one of the blacklist I use blocks a sender that does not send spam, at least to my e-mail server.