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Internet Exchange Frequently Asked Questions

Internet Exchange Messaging Server
Message Routing FAQ

Overview
Message Routing within the Internet Exchange Messaging Server (both Enterprise and Workgroup versions) is accomplished by the internal Router of the Message Transfer Agent (MTA).  The MTA is made up of the following modules:

Additional Documentation
Further information related to the routing of messages within the MTA can found in the following documents:

Questions and Answers

  1. How is inbound mail routed by the Internet Exchange Messaging Server? Is it by different domains for cc:Mail and Notes Mail or is it based on the mapping of the mail name inside the MTA?

  1. How is inbound mail routed by the Internet Exchange Messaging Server? Is it by different domains for cc:Mail and Notes Mail or is it based on the mapping of the mail name inside the MTA?

    2. The Internet Exchange Messaging Server's Preprocessor Unit first receives incoming messages from any one of the various input channels (SMTP daemon, CCOUT, NOTESOUT, BSMTP OUT, DLOUT, etc).  Once received by an input channel, the message is inserted into the MTA Input Queue (with the appropriate input queue type being noted in the message queue entry). 

    After fetching a new message from the input queue, the MTA analyzes the message recipient addresses in the envelope, to determine the appropriate output channel and possible address expansions for each recipient.   For addresses that are considered local to the MTA, recipient addresses are looked up in the local Directory for further resolution and expansion.   Non-local recipients will be assigned to the SMTPC Output Queue, assuming the message has passed the anti-relaying tests, otherwise a non-delivery message will be generated for all recipients that cannot be further routed at this point.  After looking up all recipients and assigning output channel / addresses for the inbound recipient list, a new internal envelope is created.   This new envelope contains the input channel name, the message sender address, and the output channel / recipient address pair for each final recipient.

    At this stage, all final recipient addresses (known to the local MTA) are known along with their associated output channel.  The message is now passed to the Preprocessor for any special processing such as Anti-Virus scanning, Anti-Spam checks, Disclaimer Addition, etc.  For each Preprocessor Module configured into the MTA, the Preprocessor will consult both the envelope recipient list and the Channel Action Matrices for each Preprocessor Module to determine which modules need to be run against a particular message.  Actually, the modules that need to be applied are dependent upon the Input Channel / Output Channel combinations for each message recipient. 

    After correlating the message envenlope information to each of the configured Channel Action Matrices, the appropriate Preprocessor Modules are run against the inbound message.  After preprocessing is complete, the resulting message(s) are inserted into the appropriate output shared message queues for later processing by one of the several possible output channel processors (SMTPC, CCIN, NOTESIN, DLIN, BSMTP IN, etc).