Self-hosted mail-receiver update following Let's Encrypt root certificate change

This announcement only affects self-hosters who are running Direct-delivery incoming email for self-hosted sites. Managed hosting customers, and self-hosters using POP3 for incoming mail are not affected.

As you may be aware, Let’s Encrypt recently changed their root certificate. The old root certificate expired today, and has caused a number of issues for out-of-date clients across the web. All of our systems at CDCK are up-to-date, and were not affected by today’s expiration. Unfortunately we missed the public mail-receiver docker image, which has not been updated for a few months.

This means that existing self-hosted mail-receiver installations will be unable to deliver mail to letsencrypt-secured sites.

We just pushed an updated version to DockerHub, which includes the new root certificate. Assuming you followed the official installation instructions, you can update your installation by running

docker pull discourse/mail-receiver:release
cd /var/discourse
./launcher rebuild mail-receiver

Mails received by broken installations will have been temporarily queued on the sending server. Those servers should attempt to redeliver the mail periodically, so any missed mails should arrive soon after you update the image.

If you’re still seeing issues after following these steps, make sure you’re running the release version of mail-receiver. You can find information on that in this topic.

Sorry for the disruption here! Big thanks to @wlandgraf for initially reporting the issue, and helping us test the fix :heart:


Thanks for the fix! My update got stuck with the following error message. I haven’t made any changes to this template, so I’m not sure what to do?

root@ba /var/discourse # ./launcher rebuild mail-receiver
Ensuring launcher is up to date
Fetching origin
Updating Launcher...
Updating 46d899f..990519e
error: Your local changes to the following files would be overwritten by merge:
Please commit your changes or stash them before you merge.
failed to update
1 Like

What happens if you

cd /var/discourse
git diff

Does it show any differences in the web.letsencrypt.ssl.template.yml file?

If so, you can reset them using git reset --hard


Ah, I did make a change :innocent: I got it to upgrade now, thanks!


You can test whether you’re running the old mail-receiver like this.

docker exec mail-receiver bash -c "cat /etc/issue|grep Alpine"

If it’s Alpine, it’s the old one.

docker exec mail-receiver bash -c "cat /etc/issue|grep 'Debian GNU/Linux 11'"

If it’s Debian, it’s the new one.


@david, would you mind having a look at the issues below, the latest update to the mail-receiver removed the ability to implement additional anti-spam measures, which worked wonders in the previous version, and my forum is under increasing spam pressure again due to the last change.

I tried to figure out what the root issue is, but I don’t have deep enough knowledge of postfix to figure it out. I found similar reports (client=unknown even when PTR record exists in DNS) regarding postfix in a chroot jail, so this might have something to do with it. Also, dnsutils seem to be missing from the new mail-receiver Debian image, but installing them still doesn’t fix the issue?

This one should be fixed easily:


@david Thanks for this fix! I just ran it and I can see it’s working. :+1:

Is there a way to see which emails were not able to be delivered since October 1st?

I’ve tried this, but I only see 5 requests (the earliest was received on Nov 26):

/var/discourse/launcher enter mail-receiver

I also tried looking at the logs, but I only got the warning reported here:


I think anything which isn’t still in the queue should have been bounced back to the sender. I’m afraid I’m not sure whether the container has any logs which would go back further than what you’ve found.


Would simply adding pull_image after line 657 resolve the need for explicitly pulling the image before the rebuild? I.e.

  # If the image being bootstrapped is not the base Discourse image
  if [[ ! X"" = X"$base_image" ]]; then
    # Attempt to bring the image up to date

This will cause a docker pull $image to always happen during a bootstrap/rebuild of a container with base_image set in its yml file. I don’t think that hurts for mail-receiver if it happens to already be up to date but I’m not sure if there are other situations where that could be a problem.


Yeah, an unconditional pull probably makes sense here. It’s a little strange that it only applies to our main base image at the moment. What do you think @Falco?


I’d be interested to hear a definitive answer to this question :slight_smile:

1 Like

I think you can see it by querying the incoming_emails postgres table


Unfortunately that doesn’t show anything in the relevant time period (October 2021 to February 2022).

Would there be any logs in the mail-receiver container itself?

1 Like