A backup domain MX server is required in case the primary domain MX server fails.
WorkgroupMail can be configured to receive all mail sent to it by SMTP and then to route all relevant incoming mail to another server. This type of server can act as a backup for a domain (MX) mail server.
If you receive mail directly from the internet then a backup domain mail server will receive mail when the primary server is busy or off-line. This copy of WorkgroupMail would just require the minimum five user licence and should be configured to route all mail to the Primary server. While the Primary is not available the backup server will receive and hold the incoming mail based on the fact that it has a lower priority MX record preference. When the primary comes back up on line again all the stored messages will be transferred across.
To configure WorkgroupMail to function in this way:-
1. Create a single domain that may or may not be the domain for which mail is to be routed.
2. Create a single user account and give it a mailbox that will not receive mail, eg firstname.lastname@example.org.
3. Edit the properties for the domain and configure the mail for unknown recipients to be relayed if the recipient exists in the routing table.
4. Create a routing table entry that will route all mail for your domain. Click Settings, Routing, Add, and enter the domain address with a wilcard, *@domain.com, and enter the address of the server to receive the mail.
5. Configure the Relay Control properties to be ‘This server does not relay for foreign domainsâ€¦’. No trusted hosts need to be configured for the routing action to be performed.