The da-popb4smtp (POP before SMTP) is a DirectAdmin tool. It allows POP/IMAP authenticated users to send emails without requiring SMTP authentication. It scans the mail logs and adds the IPs of POP/IMAP successfull logins to the /etc/virtual/pophosts file. The entries will be kept for 30 minutes.
As of SpamBlocker 4.5.2 (release date 2016-12-13), the tool is disabled by default, meaning that all the users must use SMTP authentication before sending emails. So, you don’t need to do anything. You can check this by looking for hostlist relay_hosts option in the /etc/exim.variables.conf.default file. The option should not have any value:
[root@web ~]# grep "hostlist relay_hosts=" /etc/exim.variables.conf.default
hostlist relay_hosts=
[root@web ~]#
It still runs to log bandwidth/connections:
[root@web ~]# service da-popb4smtp status
Redirecting to /bin/systemctl status da-popb4smtp.service
● da-popb4smtp.service - POP before SMTP daemon
Loaded: loaded (/etc/systemd/system/da-popb4smtp.service; enabled; vendor preset: disabled)
Active: active (running) since Mon 2022-01-24 03:34:21 CST; 1 weeks 2 days ago
Docs: http://www.directadmin.com
Main PID: 24307 (da-popb4smtp)
Tasks: 1 (limit: 104857)
Memory: 2.9M
CGroup: /system.slice/da-popb4smtp.service
└─24307 /usr/local/directadmin/da-popb4smtp
[root@web ~]#
In case you want to enable the da-pop4smtp tool, set the hostlist relay_hosts option in /etc/exim.variables.conf.default.custom as:
hostlist relay_hosts=net-lsearch;/etc/virtual/pophosts