Run this command
cd /usr/local/directadmin/custombuild ./build update ./build set_php imap yes ./build php_imap
Run this command
cd /usr/local/directadmin/custombuild ./build update ./build set_php imap yes ./build php_imap
Dovecot is an open source IMAP and POP3 email server for Linux/UNIX-like systems.
service dovecot start
or
systemctl start dovecot
service dovecot stop
or
systemctl stop dovecot
service dovecot restart
or
systemctl restart dovecot
service dovecot reload
or
systemctl reload dovecot
service dovecot status
or
systemctl status dovecot
chkconfig dovecot on
or
systemctl enable dovecot
vi /etc/dovecot/dovecot.conf
How to Fix the ‘Preview Could Not Be Loaded’ Error?

Probable causes:
Solutions. Try the following:
The service ‘exim’ on server xxx is currently down [Follow this]
SMTP Error (-1): Connection to server failed.
service postfix status
Unit postfix.service could not be found? Restart postfix
service postfix restart
Rebuild your exim.
cd /usr/local/directadmin/custombuild ./build update ./build set exim yes ./build set eximconf yes ./build set eximconf_release 4.5 ./build set spamassassin yes ./build update ./build exim ./build exim_conf
Start, stop and restart the Exim mail server
Start Services:
/etc/init.d/exim start
or
service exim start
Stop Services:
/etc/init.d/exim stop
or
service exim stop
Restart Services
/etc/init.d/exim restart
or
service exim restart
Status of Exim service:
/etc/init.d/exim status
or
service exim status
or
systemctl status exim.service
Edit exim conf
vi /etc/exim.conf
Helpfiles for Exim
https://help.directadmin.com/?topic=17