The IBM® Lotus® Domino® mail router (the Router) is a special server task responsible for the delivery and transfer of the messages in MAIL.BOX. Delivery refers to moving messages from MAIL.BOX into a local mail file or database; while transfer refers to sending messages from MAIL.BOX across the network to another server.
Mail routing on a Domino server begins when a mail server receives a message from a mail client, a Router on another Domino server, or an application. The message is transferred to a special IBM® Lotus® Notes® database, called MAIL.BOX, on the server. The server temporarily stores all incoming and outgoing mail in the MAIL.BOX database.
The Router periodically checks MAIL.BOX for new or changed messages. When it finds a message that requires processing, the Router reads the recipient list and for each recipient determines whether the destination mail file is on the current server or a different server. The Router then moves the message, delivering it to local mail files on the server or transferring it to MAIL.BOX databases on other servers as necessary.
When a recipient’s mail file is not on the local server, but is in the Domino domain, Domino calculates how to route the message to the recipient’s server and whether to use SMTP or Notes routing (NRPC). The configuration of the local server and the message format determines how Domino moves the message to the server. For messages in MIME format, if the local server can send SMTP within the local Internet domain and the home mail server can receive SMTP, the Router uses SMTP to send the message. Otherwise, the message is routed using NRPC.
When necessary, the Router converts the format of the message. Conversion can occur during message delivery and during message transfer. For example, if a recipient’s Person document specifies MIME storage for incoming mail, but the original message was sent in Notes rich text format, the Router converts the message to MIME before delivering it to the local recipient’s mail file. To determine whether the receiving server can handle MIME messages, the sending server checks the Server document of the receiving server to find out what version of Domino it’s running.
To minimize the number of conversions, Domino servers running Release 5 or later support the transfer of MIME messages over Notes routing. As a result, MIME messages destined for Internet recipients can route through internal servers “as is,” regardless of whether the intermediate servers use Notes routing or SMTP.