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I think I know the answer to this, but wanted to ask to make sure I'm not missing anything.

My ISP has blocked port 25 for residential customers. To keep receiving email I am using Dyn's Email Gateway service, which receives my mail and then sends it to my server on a non-standard port. I have configured my MX records and added Dyn's servers to Orf's intermediate host list.

I am receiving mail and everything appears to be working, however it appears that I've lost the ability to really be aggressive with the spam checks because all the incoming emails are from the intermediate host and the before arrival checks are skipped.

Did I miss anything in the configuration or is this just a limitation of how I have things configured? I am considering getting the "business" service plan from my ISP so port 25 will be open and I can use ORF's full functionality.


by Josh 6 years ago

@Josh: That is correct, this is a technical limitation: since emails are relayed through this Intermediate Host (and not sent to ORF directly), Before Arrival filtering (thus, the Greylisting test) cannot be used in this setup.

At Before Arrival (RCPT TO: stage of the SMTP Transport), ORF will consider the connecting host as the sender, which will always be the IP of Dyn's Email Gateway, as at that stage it does not yet know who the actual sender was - that information is stored in the email header, which is transferred at On Arrival only (DATA/BDAT command of the SMTP transport).

For more information, consult the following Help topics:

by Krisztián Fekete (Vamsoft) 6 years ago
(in reply to this post)


@Krisztián Fekete (Vamsoft): Krisztian,

Thanks for info and confirming that this is the normal behavior and limitation of using an intermediate host!


by Josh 6 years ago
(in reply to this post)

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