Our old mail system's configuration
October 16, 2007
Before I can talk about more interesting mailer things, I have to explain how our old mail system was configured.
Our old mail system makes perfect sense once you realize that it was
more or less designed around the idea that nothing should ever have
to be done over NFS. In order to manage this, each different sort of
processing had to be done on the machine that held the relevant files;
So the mail flow for incoming mail went like this:
Mail routing was done by rewriting the destination addresses. Partly as a result, the postbox and oldmail machines only did their delivery for addresses in magic forms; if you sent other mail to them, they passed it back to the central mail machine.
(The fileservers passed email for the outside world back to the central machine instead of trying to deliver it directly. This had both good and bad effects.)
One consequence of this design is that all of the machines involved had
to NFS export things to our login and compute servers, because they
all had local storage. The postbox machine had to export
(Conveniently, the postbox machine was also the IMAP/POP server, so that bit didn't have to worry about mailbox locking over NFS.)
There was a separate mail submission machine for outgoing user email, whether from our servers or from user PCs. It forwarded mail for local destinations to the central mail machine and otherwise sent the mail directly to the outside world.
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