Do some MTAs look up the hostname given in HELO and reject mail as possible spam if the HELO hostname and the IP address do not match?
Yes, but that's a very unreliable thing to do.
It is more reliable to reject specific HELO arguments (like your own name, your own IP address, and 'oemcomputer' ) instead, because there are a number of situations where a HELO that does not resolve or resolves to something other than the connecting IP is really quite normal and necessary. For example, if you have a load-balanced cluster of outbound mail machines all sitting behind a NAT device that makes them look like they are coming from one address, it is good to have them HELO as their own names, even though those names probably are not even resolvable to the world at large.
-- Bill Cole [EMAIL PROTECTED]
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