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Mail on Open Food Facts infrastructure

Because mail is difficult to setup, we use Proxmox Mail Gateway as a relay to all servers. It ensure correct SPF, but also it adds DKIM signature.

No server receive mail, but they should be able to send them.

📝Note: We ONLY support emails address on primary domain (openfoodfacts.org) and we DO NOT support emails on sub domains (aka xxx.openfoodfacts.org).

Google Workspace

We use Gmail for email boxes and groups.

We have a DKIM record configured for google domain and sub-domains in the DNS, we also take into account in SPF rule. You can find the public key in google workspace admin console, under gmail.

Brevo

We use Brevo to send newsletters.

We have a DKIM record configured for the Brevo domain in the DNS, we also take into account in SPF rule. You can find the public key if you are logged as admin in Brevo.

Proxmox Mail Gateway

This is the pmg lxc VM (aka 102) currently on ovh1.openfoodfacts.org. The install follows procedure starting from a debian distribution.

Administration

You can access the administration of pmg by using a tunnel on ovh1:

ssh  -L 8006:10.1.0.102:8006 ovh1.openfoodfacts.org -N

then connect to https://localhost:8006 (beware the s of https !)

You must have an account to connect to the service.

The most important tools you will find is Administration where you can see queues of deferred mails or logs (on the administration entry).

See https://pmg.proxmox.com/pmg-docs/pmg-admin-guide.html#_administration

Notable configurations options

First bare in mind that even if proxmox mail gateway is built to handle outgoing and incoming emails, we want to use it only for outgoing emails.

We registered an letsencrypt account with [email protected]

Administrator email is [email protected]

Relay is set to smtp-relay.gmail.com, although we should not need it (this is for incoming mails).

SMTP private port is set to 25 and public port to 26

In networks tab, there are all servers ips, though because of redirects, PMG sees each incoming request as issued by 10.1.0.1.

TLS (TLS tab) is enabled

DKIM is configured with label pmg-openfoodfacts, with a key size of 2048, the public key was reported in DNS configuration

see also installation report

redirects

On DNS:

  • pmg.openfoodfacts.org is a CNAME to ovh1.openfoodfacts.org
  • ovh1 ip address is reported in the spf entry of the DNS
  • there is an entry for the dkim key

An iptable rule on host (ovh1) redirects our server incoming ips to the VM smtp port (25). Private network address (corresponding to VM and docker ranges) are also redirected.

To add a new machine

sudo iptables -t nat -A PREROUTING -s 213.36.253.206,213.36.253.208,146.59.148.140,51.210.154.203,1.210.32.79 -d pmg.openfoodfacts.org -p tcp  --dport 25 -j DNAT --to 10.1.0.102:25

don't forget to save iptables

(a generic masquerading rule for VM also exists)

Note that the port 25 is in fact the private (trusted) port (not the public one, as we are not receiving emails). This is a tweak in default config.

Also the nginx reverse proxy (VM 101 on ovh1) proxies requests to pmg.openfoodfacts.org on port 80, to the proxmox mail gateway VM (102), this is needed for certificate generation through letsencrypt by the gateway.

Testing that the gateway is well configured

To do a simple test, you may use:

echo "Subject: mail gateway test" | sudo sendmail -f [email protected] -v [email protected]

directly on the pmg server.

To test quality of the configuration we can send a mail to a service such as https://www.mail-tester.com/

To test using this service:

  • I temporarily added an iptables rule to enable my personal ip address to be forwarded to the mail gateway (as for servers)
  • I added pmg.openfoodfacts.org as an smtp server in thunderbird and configured my personal address to use it
  • I sent a mail as requested by the service
  • I could then check the result
  • I undo iptables and thunderbird config

Servers

On client servers (be it a VM, a host or a standalone server), we use either exim4 or postfix.

Email aliases

We normally keeps a standard /etc/aliases. We have specific groups to receive emails: [email protected] and [email protected]

You may add some redirections for non standard users to one of those groups. Do not forget to run newaliases, and etckeeper.

Postfix configuration

Run: dpkg-reconfigure postfix:

  • configuration type : satellite system

  • mail name: openfoodfacts.org

  • relayhost: pmg.openfoodfacts.org

    (with an exception for ovh1/ovh2/ovh3: 10.1.0.2)

  • mail for root: [email protected]

  • other dest: blank

  • sync: no

  • local network: leave default

  • use procmail: no

  • default for the rest

IMPORTANT: On some system, the real daemon is not postfix.service but [email protected]

(so eg., if you touch /etc/alias (with after sudo newaliases) you need to systemctl reload [email protected]

Exim4 configuration

Run: dpkg-reconfigure exim4-config:

  • mail sent by smarthost; no local mail
  • mail name: openfoodfacts.org
  • listen: 127.0.0.1
  • other dest: off1.free.org
  • visible domain name : openfoodfacts.org
  • IP address smarthost: pmg.openfoodfacts.org
  • keep DNS queries minimal (dial-up): no
  • local: maildir format in home
  • split config : no

Testing

To test that mail is well configured, you can use:

echo "Subject: sendmail test xxx" | sudo sendmail -f [email protected] -v root

or, with the bsd-mailx package installed 1:

echo "test message from xxx" |mailx -s "test root xxx" -r [email protected] root

If you do not receive the email on expected group, here are some checks:

  • look at logs on your server:
    • /var/log/exim/ if you use exim4
    • /var/log/mail* if you use postfix
  • look at logs on pmg VM:
    • /var/log/mail*
  • ping pmg.openfoodfacts.org to verify network
  • nc -vz pmg.openfoodfacts.org 25 suceed, else you might have firewall problems: verify iptables on your machine and on ovh1. (nc command belongs to netcat-traditional or netcat-openbsd packages)
  • you can even try to send a mail manualy using smtp protocol using nc pmg.openfoodfacts.org and following a tutorial about sending email with netcat If it suceed this may mean you have a problem in username to email address translation.
  • /etc/mailname contains openfoodfacts.org (see also debian wiki)
  • check /etc/aliases and /etc/email-adresses if you use exim4

Note that we use bsd-mailx and not the alias from mailutils as it does not behave the same. Noticabely it won't use /etc/mailname to complete email address which leads to problems.

References

Footnotes

  1. ↩