A technical description of the communication between KDE clients and the Kolab server follows.
The protocols were selected with the following criteria in mind:
proper standardization e.g. by the Internet Engineering Task Force (IETF, http://www.ietf.org) open standard in the sense of the term open source existing free software implementations must scale very well in general simplicity over complexity - in other words limitation to a small set of well-established and widely used protocols
This leads to the following choice of protocols used in the project:
Lightweight Directory Access Protocol Version 3 (LDAP, IETF RFC 2251)
File Transfer Protocol (FTP, IETF RFC 765)
Simple Mail Transfer Protocol (SMTP, IETF RFC 2821), SMTP over Secure Socket Layer / Transport Layer Security (SMTP over SSL/TLS, IETF RFC 2246)
Internet Message Access Protocol (IMAP, IETF RFC 1730), IMAP over SSL/TLS (IETF RFC 2595)
Post Office Protocol Version 3 (POP3, IETF RFC 1939), POP3 over SSL/TLS (IETF RFC 2595)
Hyper Text Transfer Protocol (HTTP, IETF RFC 2616), HTTP over SSL/TLS (IETF RFC 2818)
HotSync Protocol (this does not meet some of the above criteria but seems to be widely accepted and free implementations exist)