Administrator's Guide - Kerio Software Archive

27.5 Setting up the backup mail server4. In Configuration → Domains section of the Kerio MailServer administration console (chapter7.5), specify message forwarding to the mail1.company.com primary mailserver (seepicture 27.5).There are multiple ways of forwarding messages:• The best way of setting up forwarding from the backup server is to set the primaryserver in the way that it queries the secondary server regularly using the ETRN command.This procedure saves time because the servers are not connected to an unavailableprimary server. The primary server must support the ETRN command.Kerio MailServer supports using the ETRN command for requesting emails (see chapter15.5). If you use Kerio MailServer as a primary mailserver, we recommend thisoption. Kerio MailServer also sends the ETRN command to different servers upon eachserver startup and thus all mail is downloaded to the server in the shortest possibletime after failure.If you want to use this method of email forwarding, allow the Offline delivery — deliveryis triggered by ETRN command from remote host option (see figure 27.5) thecompany.com domain on the backup server in the administration console (Configuration→ Domains).Figure 27.5 Setting up the backup server — the ETRN commandIt is also necessary to enable using the ETRN command in the primary mailserver (seechapter 15.5) and schedule sending the ETRN command (see chapter 9).• Another possibility is setting up the rules for outgoing messages (see chapter 15.2).However, in case of unavailability of the primary server, the server will repeatedlyattempt to deliver emails, until the primary server is up and running again, which canoccasionally cause overloading of the primary server.If you prefer this method of setting the secondary SMTP server, we recommend toextend the interval for message resending. This can be set in Configuration → SMTPServer, on the Queue Options tab.In the domain configuration window, it is necessary to set name or address of theprimary server, traffic port and the Online delivery — deliver the messages immediately(see figure 27.6).• The last method is to set up the scheduler so that it adjusts the intervals for sendingemails. This setting is similar to the previous one, because the server again uses therules for the outgoing message queue. However, in this case, the interval is adjusted301