Discourse/mail-receiver:release Docker image appears to be outdated

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Update: I tested the current main branch

I built the current main branch locally and found another issue.

The old Docker Hub release image still runs the old fast-rejection code and fails during RCPT with:

450 4.7.1 Recipient address rejected: Internal error, API request failed

However, the current main branch has already removed the smtp_should_reject / fast-rejection implementation. After building main, Postfix instead fails with:

warning: connect to private/policy: No such file or directory
451 4.3.5 Recipient address rejected: Server configuration problem

I traced this to two remaining references in the Dockerfile:

check_policy_service unix:private/policy

The policy service itself has been removed, but smtpd_recipient_restrictions still references its socket.

I removed unix:private/policy from smtpd_recipient_restrictions, rebuilt the image, and incoming SMTP mail was then accepted successfully.

After switching to a Global API Key, delivery to Discourse also succeeded:

dsn=2.0.0, status=sent (delivered via discourse service)

So there seem to be two separate issues:

  1. The published discourse/mail-receiver:release image is outdated and still contains the old fast-rejection implementation.
  2. The current main branch removed that implementation, but the Dockerfile still configures Postfix to use unix:private/policy.

There may also be a separate issue with granular API keys: a key scoped only to receive emails returned HTTP 404 from /admin/email/handle_mail, while a Global API Key returned HTTP 200.

I can submit a PR for the two stale private/policy references in the Dockerfile if that would be helpful.

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