Administrator's Guide - Kerio Software Archive

Chapter 6 ServicesMax. number of concurrent connectionsThis option limits the number of concurrent connections to the selected service. Toomany concurrent connections may cause the server overload which can subsequentlylead to its failure. This is also the main idea of the so-called DoS (Denial of Service) attackwhere the attacker tries to overload the server by too many concurrent connections. Settingthe limit for the number of connections therefore helps to prevent the DoS (Denialof Service) attacks against your server.Warning: When you plan to limit the number of connections, consider the number ofserver users.6.2 Important NotesNon-secure and secure versions of the same service act as two separate services. This meansthat there are two different ways of accessing the same server and the user (client) can choosewhich one to use. For security and privacy protection reasons we strongly recommend usinga secure version of any communication means. However, this must be supported by clientsoftware.IMAP and HTTP access the same IMAP account in the same way. These two services can bothbe used (one at a time) without any limitations or risk. POP3 and IMAP/HTTP access thesame physical account but POP3 can only retrieve messages stored in the INBOX folder, as itcannot “see” other folders. All incoming messages are stored in the INBOX folder. POP3 alsodownloads all messages from the server to the client machine. This can lead to the followingcomplications:1. If a user logs into the account using POP3 first, all messages from the INBOX folder willbe downloaded to his/her machine. After logging in using IMAP, these messages will nolonger be at the server.2. If a user logs into the account using IMAP first (or uses HTTP) and moves messages toa folder other than INBOX, these messages will not be downloaded later using POP3.3. If a user has set rules such that all messages are moved to different folders, no messageswill be accessible via POP3.6.3 TroubleshootingWhen solving problems regarding services, logs of the traffic between the server and clientsmight be helpful. To log relevant information, enable a corresponding option under Logs →Debug in the Kerio Administration Console:1. In the Kerio Administration Console, go to the Logs section and select the Debug log.2. Right-click on the log pane to open a context menu, and select Messages.3. In the Logged Information dialog just opened, enable logging for the particular service (seefigure 6.5).60