Emails not getting signed by DKIM when sent using discourse

Product Support Self-hosting

AI-generated summary

The user o_o1 experienced issues with DKIM signing for emails sent from Discourse, as they were not being signed properly when using an external SMTP server (DirectAdmin with Exim). Initially, emails sent via Thunderbird were successfully signed with DKIM, but those sent through Discourse showed no selector or domain in the DKIM check. supermathie clarified that Discourse acts as an SMTP client, so DKIM signing must be handled by the receiving SMTP server, not Discourse itself. Thomas_Rother reinforced this point. After updating DNS TXT records in Cloudflare and adjusting rDNS, the user retested and found DKIM signing working correctly. o_o1 speculated that the issue may have been resolved due to DNS propagation or cache clearing, and confirmed that the problem is now resolved.

1

I have discourse installed on VPS
I have directadmin installed on a different managed VPS running exim smtp

In discourse I used SMTP server details on the directadmin VPS

I checked emails with isnotspam.com

Sending email using thunderbird with directadmin SMTP

Result: pass
ID(s) verified: [header.From=discourse@example.com](mailto: header.From=discourse@example.com)
Selector=x
domain=example.com
DomainKeys DNS Record=x._domainkey.example.com

BUT if I send it out using discourse the result passes, but no selector

Result: pass
ID(s) verified: [header.From=discourse@example.com](mailto :header.From=discourse@example.com)
Selector=
domain=
DomainKeys DNS Record=._domainkey.

Any ideas?

2

Which component are you expecting to be doing the DKIM signing?

3

My SMTP server should.

However when emails are sent from discourse it’s not getting signed the same.

I’m wondering if it has to do with the helo forum.example.com

4

You gave the answer yourself :sunglasses: Discourse acts as an smtp client and the dkim signing must be provided by the smtp server receiving the mails from Discourse.

5

Yes correct.

So the different signing results when checked with isnotspam was confusing me.

Anyway , I re ran the test today and now it passes

–

----------------------------------------------------------
DKIM check details:
----------------------------------------------------------

Result: pass
ID(s) verified: header.From=discourse@example.com
Selector=x
domain=example.com
DomainKeys DNS Record=x._domainkey.example.com

Not sure what happened, but I did have to update my DNS txt key inside cloudflare, as well as update the rDNS for the mail server.

Maybe it just required time for everything to propagate or clear some cache?

6

In the previous test:

Result: pass
ID(s) verified: [header.From=discourse@example.com](mailto :header.From=discourse@example.com)
Selector=
domain=
DomainKeys DNS Record=._domainkey.

there was no DKIM record, so it wasn’t signed.

DNS doesn’t propagate, remember.

Regardless, now the mail is signed so you should be good?

7

Yep its signs on checking, so something needed cache updating