Why forwarding is a Bad Thing

Jim Reid jim at rfc1035.com
Fri Mar 23 15:24:42 UTC 2001

>>>>> "Brad" == Brad Knowles <brad.knowles at skynet.be> writes:

    >> For example in most mail systems, it is trivial to configure
    >> them to send all non-local mail (for some definition of local)
    >> to a smart mail relay.

    Brad> 	True enough, but then you're hard-coding by name what
    Brad> your outbound mail relay(s) is/are.

This is no big deal. Just change the A or MX record and the migration
from old relay to new relay is done for everyone.

    Brad> 	However, one thing I still don't understand is how
    Brad> doing that sort of thing is significantly different from
    Brad> hard-coding your outbound mail relay(s), and yet one is
    Brad> "evil" and the other is not.

Well with mail forwarding/relaying, it's done on name, not IP address.
This is a big win. The configurations don't have to change if the
mailhub moves. Make one DNS change and it's done.

And there are usually other criteria -- value-added functions like
billing, virus scanning, content control, anti-spam checks, etc --
which make centralised mail relays attractive or mandatory. I have
also seen central mail relays helping to route mail more efficiently
into enterprise-wide mail solutions like Notes or Exchange.

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