Howdy, In 18.104.22.168 there may be an issue in situations where /proc resections are enabled in the gresec kernel with mailman. This may prevent mailman from sending messages. To see if this issue affects you, review your kernel configuration file for items like these. CONFIG_GRKERNSEC_PROC=y CONFIG_GRKERNSEC_PROC_USER=y CONFIG_GRKERNSEC_PROC_ADD=y Server administrators who are experiencing this issue can use the following workaround. Code: echo "127.0.0.1" >> /etc/skipsmtpcheckhosts If you are having this issue please open feel free to open a ticket with us via https://tickets.cpanel.net/submit/index.cgi?reqtype=tickets and we would like to investigate further. Thanks!