NullLogic Groupware is a modular Web-based groupware and email system designed for contact management and event scheduling. Additional features include private messaging, public discussion forums, webmail, shared bookmarks, file sharing, call tracking, order processing, an XML-RPC API, and integrated POP3 and SMTP servers.
SMTP client class is a PHP class that connects to a mail server to send messages. It can relay message delivery to a defined server or directly deliver messages to a recipient's server for urgent message delivery. It supports secure connections with SSL or starting TLS after the connection is established, connection timeouts, authentication using PHP SASL class (PLAIN, LOGIN, CRAM-MD5, NTLM), POP3 before SMTP delivery authentication, and takes advantage of the SMTP PIPELINING extension to buffer SMTP commands, providing much faster queueing of messages when delivering to a large number of recipients (bulk mail).
NS WebMail offers standard mail functions for POP3 inbox management. Mail is sent using SMTP protocol. It has been designed to be light and simple, to avoid having to use heavy IMAP or SQL servers, and it has full MIME support for incoming and outgoing mail. It is Perl-strict and mod_perl-compliant, and has security using HTTP authentication or cookies. LDAP connectors are also available (as optional plug-ins) for authentication and read-only address book. Two interfaces are available (with and without frames). It is able to recognize tags from spam detection software (Spamassassin is supported out of the box).
KONSEC Kolab Server is a highly scalable, cluster-capable messaging and collaboration server that is based on the outstanding open source project, Kroupware. The KONSEC Konnektor is a simple client extension that gives Outlook complete group functionality through the Kolab Server, which employs the open standard IMAP together with ACLs, thus enabling you to collaborate in a unique mixed Windows/Linux environment.
Zimbra is a next-generation enterprise messaging and collaboration system. It features an Ajax Web client with conversation views, fast email search, Web service mash-ups, shared calendars, document authoring, and IM. The server also syncs to MS Outlook (via MAPI), the Apple desktop (via iSync, iCal, and CalDAV), POP/IMAP clients, and mobile devices (BlackBerry, smart phones, HTML Web browsers). A version of the Web client, Zimbra Desktop, also works offline with any POP/IMAP server. Administrators can control live backup/restores of individual or groups of mailboxes, hierarchical storage (HSM) and clustering, LDAP directory configuration, Web services integration with existing enterprise applications, and integrated anti-spam and anti-virus.