Kerio Connect - Administrators Guide - Kerio Software Archive

Protecting SMTP the server in Kerio ConnectHow to configure security options of the SMTP serverIn Kerio Connect, you can configure several limits for IP addresses. This can be done in theadministration interface in section Configuration → SMTP Server → tab Security OptionsFor a single IP address, you can set:• Maximum number of messages sent in one hour — any new message sent from the IPaddress where the limit was exceeded in the recent our is discarded• Max. number of concurrent connections — protection from so-called DoS attackswhich overloads the server• Maximum number of unknown recipients — protection from so-called directoryharvest attacks when an application connects to your server and uses dictionary togenerate possible usernamesFigure 2SMTP serverSelect a group of trusted IP addresses which will not be affected by these settings.With the following additional options you can:• Block messages if the sender’s domain does not have a DNS record (or revers DNSentry) — protection from senders with fictional email addresses• Require authentication even when sender is from a local domain — ensures theauthenticity of anyone sending from a local domain• Set maximum number of recipients per message — protects from spam messages setto a large number of recipients• Maximum number of failed commands in SMTP session — spam is often sent byspecial applications that connect to SMTP servers and ignore its error reports. Kerio94