Read this section if you need to provide special relaying features.
If you place an alias record into the Router table:
NoRelay:<user> = email@example.com
then all mail from strangers to that user will be rerouted to that other.host server. If that server address is not included into the Client IP Addresses list, these messages will be treated as messages "from a stranger to a stranger", and they will be rejected if the Relay for Clients Only option is switched on.
To enable relaying, use the Relay: prefix:
Relay:<user> = firstname.lastname@example.org <user> = email@example.com
When an address is being converted with such a record, it gets a marker that allows the server to relay messages to that address. If an address is modified with a record that has the NoRelay: prefix, this marker is not set, but it is not reset either - if it has has been set with some other Router record (see the example below).
The same situation exists if you want to reroute all mail for a certain domain to a different host (for example, if you back up that host), and that host address is not included into the Client IP Addresses list.
Relay:clienthost.com = client1.com Relayt:<*@clienthost.com> = client1.com
When the address modified with the Router record is not a "simple address", i.e. it contains several routes, as in user%host1@host2, or <@host2:user@host1> - the Relay: prefix does not set the flag that allows message relaying. This is done because the host to which the rerouted message is relayed may "trust" all messages that come from your host, and relaying addresses with multiple routes would allow someone to relay messages to anybody through your host and that other host.
If the receiving server is well-protected, too, you may need a Router record that allows relaying of any address rerouted with that record. Use the RelayAll: prefix for those records.
Very often you do not want the Router records to be used for actual relaying - you provide them for your own clients only, to specify a special path for certain addresses/domains. For example, if you want mail to bigprovdier.com to be sent via a particular relay relay3.com, you should place the following record into the Router table:
NoRelay:bigprovdier.com = firstname.lastname@example.org._via
Without the NoRelay prefix, any host on the Internet could send messages to bigprovdier.com via your Server. The NoRelay prefix tells the Router not to add marker to addresses in the bigprovdier.com domain, so only your own users (clients) can send mail to bigprovdier.com domain using your Server.
Note: you may have an alias record in your Router:
Relay:<joe> = email@example.com
This record tells the server to reroute all mail addressed to firstname.lastname@example.org to email@example.com. Since this record has the Relay: prefix, anybody in the world can send E-mail messages and Signals to firstname.lastname@example.org and they will be successfully relayed to the bigprovdier.com domain.