Administrator's Guide - Kerio Software Archive

Chapter 6 Services• SMTP on port 25 with STARTTLS — traffic on port 25 is started as unencrypted. Ifboth sides support TLS, TLS is started via STARTTLS. Otherwise, the traffic is heldunencrypted.• SMTP with SSL/TLS on port 465 — the traffic is encrypted right from the start.Warning: If traffic between Kerio MailServer and mail client is running on port 25, a problemmight occur with email sending. Since public WiFi networks often do not supporttraffic on unencrypted protocols, SMTP on port 25 can be blocked. In such case userscannot send email out of the network. However, SMTPS on port 465 is usually allowed.Therefore, it is recommended to keep SMTPS connection enabled so that notebook andApple iPhone users can use this port to connect to the server. It is also necessary thatusers’ email clients (SMTPS encryption and traffic port) are set correctly.POP3POP3 protocol server (Post Office Protocol). This server allows users — clients to retrievemessages from their accounts. It is also often referred to as the incoming mail server.Secure POP3 is a POP3 server whose communication is encrypted by SSL. The encryptionprevents the communication from being tapped.IMAPIMAP protocol server (Internet Message Access Protocol). This server also allows users toaccess their messages. With this protocol, messages stay in folders and can be accessedfrom multiple locations at any given time.Secure IMAP is an IMAP server whose communication is encrypted by SSL.NNTPNNTP protocol (News Network Transfer Protocol) — transfer protocol for newsgroupsover the Internet. The service allows users use messages of the news type and use theprotocol to view public folders.Public folders cannot be viewed via NNTP protocol if its name include a blank space orthe . sign (dot).Secure NNTP is the NNTP server version whose communication is encrypted by SSL.LDAPSimple LDAP server that enables users to access centrally managed contacts. The LDAPserver provides read-only access to the information; you are not allowed to create noredit the existing ones.Secure LDAP is an LDAP server whose communication is encrypted by SSL.If Kerio MailServer is installed on a server which is used as a domain controller (in ActiveDirectory), it is necessary to run LDAP and LDAPS services on a non-standard port or todisable them.HTTPThe HTTP protocol is used for:1TLS is follower of the SSL protocol, it is actually SSL version 3.156