Casper

> How certain we be that this test really is flakey and it's not the PR's fault? We merged a lot PRs in the last days and this test was...

Yes, with this commit [94a72dd](https://github.com/docker-mailserver/docker-mailserver/pull/2443/commits/94a72dd52cb43a8d89ca98fc7aff49c832348714)

I see, you add more and more Mac specific workarounds. This will be a cat & mouse game forever. Every PR is only tested against linux. So it's just a...

If already other (big) projects are using this restriction successful for a longer time, it seems to me, that this could also be a sane default for our next major...

LGTM 👍 The only thing I am personally not completely confident with is the var handling in `variables.sh`. While I understand your intention, I think it's too fine grained and...

> The concern may be valid, but don't go changing ENV for now as this is for 11.2 and would be a far larger change to make and review the...

I just gave it a try and added `reject_unknown_client_hostname` to my configuration. I was able to send mails from another container that is on another docker network. Relevant logs: Details...

Update from my setup: Lots of rejected SPAM Mails with 0 false positives so far 👍

IMO this can be in version `11.2`: As written, I had zero false positives with that setting. So in my experience it's a valuable anti-spam improvement that should be better...

Does your host have IPv6 connectivity? That might explain the NAT: https://docker-mailserver.github.io/docker-mailserver/edge/config/advanced/ipv6/