The Zimbra Server uses several open source projects (see the section, "Included open source projects"). It exposes a SOAP application programming interface to all its functionality and is also an IMAP and POP3 server. The server runs on many Linux distributions. It also can be run on a Windows Server, using a virtual machine and using container technology. It supports CalDAV, CardDAV and SMTP for messaging, LDAP for directory services, and Microsoft Active Directory (AD). Zimbra uses Postfix for its MTA functionality. It includes technology from ClamAV, SpamAssassin and DSPAM for anti-malware features and S/MIME for email signing and encryption. OS X Server support was dropped with version ZCS 7.0.