A full-featured SMTP server which allows multiple independent local domains, virtual addresses (aliases), to receive email via ETRN, etc. Outgoing email can be sent either directly to target domains (according to MX records in DNS) or via a parent SMTP server (e.g. the ISP's SMTP server).

POP3 (Post Office Protocol version 3) is an Internet protocol that allows a client to download mail from a server and store it on the local computer. It is suitable for clients who don't have a permanent connection to the Internet.

Unlike Internet Message Access Protocol (IMAP), POP3 does not allow users to manipulate messages at the server. Mail is simply downloaded to the client where messages are managed locally. POP3 provides access only to a user's INBOX; it does not support access to public folders.

IMAP4 (Internet Message Access Protocol version 4) is an Internet messaging protocol that enables a client to access email on a server rather than downloading it to the user's computer. This architecture allows the user to access his/her mail from multiple locations (messages downloaded to a local computer would not be available from other locations).

It is possible under certain conditions to access the email account using both IMAP and POP3 protocols.

NNTP (Network News Transfer Protocol) is a protocol used to transfer news messages and display public news folders for users. An NNTP server stores archives of all newsgroup posts.

The built-in HTTP server allows remote access to the user account. It allows reading and writing of email messages, events and tasks, folder management and modifications of personal settings. No email client software needs to be installed and no settings are needed. All the user needs is a web browser. Kerio WebMail is address in a stand-alone document, Kerio MailServer, User's Guide.

In Kerio MailServer you can manage private and public contact lists (users' data, such as email addresses). Users can access their mail and contact lists via any supported email client or Kerio WebMail interface.

The Kerio MailServer's built-in Free/Busy server is a server using HTTP to provide information on busyness and free time of other Kerio MailServer users without details of individual events being displayed.

Kerio MailServer includes tools for keeping and administration of private and public folders with calendars, tasks and notes. In the Kerio WebMail interface and the MS Outlook application with Kerio Outlook Connector, calendar, task and note folders can be managed (see chapter 32.2  Kerio Outlook Connector).

The secure LDAP service allows remote clients to search public and private contacts. Most email client programs support this feature of LDAP.

Kerio MailServer supports user administration via web interface. This way, clients of ISPs can access user mailbox, groups and aliases settings from within their domains.

The mail server can automatically retrieve email from one or more accounts located at external servers (e.g. domain account at the ISP) and deliver this mail to local accounts or sort it according to defined rules.

All Kerio MailServer services offer standard non-secure connections and SSL-encrypted secured connections. It is also possible to send messages via a secured connection, provided that the destination server supports this feature.

All incoming mail can be checked for viruses. Several actions can be taken if a virus is detected: the infected attachment can be removed, the mail can be sent back to the sender, a notification can be sent, the message can be sent to the system administrator, etc. Antivirus control is performed by an external antivirus program (such as AVG, NOD32, etc.). In addition, certain types of attachments can be filtered (by file extension — e.g. exe, com, vbs, etc. or by MIME type — e.g. application/x-msdownload) regardless of whether or not they are infected by a virus.

The mail server can be protected from spam email misuse. Messages can be detected and filtered by the SpamAssassin antispam filter, Bayesian filter, SMTP spam-server databases, checking “e-mail policy” records and/or by your own spam rules which can be set in the Spam Eliminator section.

Kerio MailServer can make backup copies of all email (or just sent email) either locally or to a remote server.

Kerio MailServer can create backups of user folders (the store directory) as well as mailserver configuration files in predefined time intervals.

Each user can define a range of actions to be performed after a message is received (moving a message to a specific folder, filtering, cellular phone notification, automated reply...). Actions can be applied to all messages or selectively by the sender's or recipient's address, subject, etc.

The server administrator has absolute control over whether messages are to be sent immediately or at given times or time intervals . This makes it possible to minimize connection costs (with dial-up lines).

Any number of mailing lists can be created within each local domain. List members can be defined by the server administrator, approved by a moderator or they can be added automatically through email. Each list can have one or more moderators who control user participation, message deliveries, etc.

Kerio MailServer has a highly configurable mailing list archive feature.

Kerio MailServer provides full support for Microsoft Active Directory as well as Apple Open Directory. It is not necessary to import user accounts into the internal database. To add or remove user account/group use the Active Directory or Open Directory system tool.

Kerio Outlook Connector is an extension to MS Outlook that uses an open MAPI interface. It is used for communication between Kerio MailServer andMS Outlook. It enables storing of various folder types (such as email messages, contacts, calendars, tasks and notes) at the server. It is also possible to share and map folders, as well as set up message sorting rules.

Kerio Outlook Connector (Offline Edition) is an extension to MS Outlook that uses an open MAPI interface. It is used for communication between Kerio MailServer andMS Outlook. It enables storing of various folder types (such as email messages, contacts, calendars, tasks and notes) at the server. It is also possible to share and map folders, as well as set up message sorting rules.

Kerio Outlook Connector (Offline Edition) allows offline users to work with their email, calendar and other groupware tools in offline mode.

Kerio Synchronization Plug-in is an add-on to MS Outlook that provides basic groupware features using IMAP and POP3 accounts. Kerio Synchronization Plug-in is available also in offline mode, providing the possibility to connect to Kerio MailServer and synchronize changed data.

Kerio MailServer provides support for the Windows Calendar application. Users can subscribe and publish calendars in Kerio MailServer.

Kerio MailServer provides support for Microsoft Entourage email client. It allows saving email folders, contact and calendars on the server. This support also allows use of the Kerio MailServer's Free/Busy server .

For communication with MS Entourage, Kerio MailServer uses the WebDAV protocol. Therefore, the HTTP service must be running on the server.

Kerio MailServer supports certain groupware features in Apple Mail 10.4.

Kerio MailServer supports subscription and publishing of iCalendar calendars. This support enables subscription of Kerio MailServer calendars to Apple iCal as well as publishing of Apple iCal calendars in Kerio MailServer.

The Apple Address Book application support allows users to search the LDAP database used by Kerio MailServer. In Apple Address Book version Apple Mac OS X 10.3, users can also synchronize contacts.

Kerio Sync Connector for Mac is a special application which enables synchronization of local data between Kerio MailServer and the Apple iCal or the Apple Address Book application.

Support for the CalDAV protocol enables subscription and viewing of calendars saved Kerio MailServer in email or calendar clients supporting CalDAV (e.g. Apple iCal). The protocol also supports meeting scheduling (Free/Busy and invitations) and subscription of delegated calendars.

Kerio MailServer provides support for Apple iPhone devices. This support allows to send and receive email and synchronize calendars and contacts with the desktop mail client.

Kerio MailServer supports running of Kerio WebMail on Apple iPhone in both the full version and the simplified version designed for PDA and mobile devices.

Support for the ActiveSync protocol allows to synchronize email, contacts, calendars and tasks between Kerio MailServer and mobile devices (PDA, Smartphone). Synchronization can be performed between the server and a mobile device (only if an application is installed on the mobile device that provides synchronization over ActiveSync).

The support also applies to synchronization between a desktop application (MS Outlook) and mobile devices. The synchronization will be performed between the desktop application and a mobile device.

Warning: To ensure that the synchronization is performed also at the server's side, MS Outlook must be extended by the Kerio Outlook Connector or the Kerio Synchronization Plug-in.

Kerio MailServer supports RoadSync, an application which allows direct synchronization of email, contacts and calendar in mobile devices via ActiveSync. The application and the mobile devices settings are focused at http://www.dataviz.com/.

Kerio MailServer allows simple migration of user accounts from various types of email servers to Kerio MailServer (e.g. from 4D or MS Exchange Server). Migration is performed by special utilities available on demand at Kerio Technologies.