Electronic mail or commonly called e-mail is a mailing service that uses computer network for sending and receiving mail. On the other hand, e-mail mostly used as one of the supporting media for any communication activities. Therefore the purpose of this research is applying auto backup email system on mail server at Unisma Bekasi software laboratory. Mail server used is Zimbra open source with Ubuntu Linux 14.04 operating system. To support the necessary elements, the bind9 system is used for naming the domain name that provides addressing on the server system. By having cronjob feature on Webmin, it makes a solution automatically command for auto backup which is combined with scrip. User account capacity and mailbox on mail server Zimbra can accommodate bigger mail compared to other servers such as qmail or postfix. Key words: mail server, open source, zimbra, cron job, auto backup.