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Re: Can you ever reject mail based on RFC2821 MAIL FROM?

2004-04-24 18:26:09

On 4/24/04 at 12:05 AM -0700, Harry Katz wrote:

Greg Connor [mailto:gconnor(_at_)nekodojo(_dot_)org] wrote:

In general, an MTA should either be an agent for the sender, or an agent for the receiver. Third-party MTAs don't get involved just on a whim; either the sender or the receiver asked for them to be involved. If a receiver wants to receive forwarded mail, the forwarder needs to comply, or they need to make an exception for that forwarder.

But as I noted above, the receiver can't make an exception (i.e. whitelist) because the forwarder doesn't appear in the MAIL FROM. So that means all forwarders have to rewrite.

No. The receiver must whitelist based either on the IP address of the forwarder or on the HELO domain. This does mean that you can't just set up a .forward to a receiving system that implements MARID checking without the admin of that system doing such a whitelist entry.

In the future, you could use the ORCPT parameter as the check if folks would implement it for forwarding.

To go back to your original question, yes, you can reject mail based on 2821 so long as you are willing to tell your users "You can't forward to here unless you tell me from where you're forwarding."

pr
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Pete Resnick <http://www.qualcomm.com/~presnick/>
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