DKIM mandatory at

Installed Delta Chat app on Android 14 device successfully.
Registered a test email address on successfully.
Tried to send an ordinary email from my standard email account to this address just to see if it shows up in the Delta Chat app.
After a while got an error messages at my standard email address like:
“Missing DKIM…”.

Is DKIM for Delta Chat or the email server at mandatory?
And if yes I doubt the usdefulness of Delta Chat. Many email provider do not support DKIM (but SPF).

Or do I miss something?

Michael was indeed recently configured to only accept mail that has a valid DKIM signature. Delta chat itself does no.such checks. If you use delta chat with an email.server that does not require a valid DKIM signature then it will work.

The reason for the nine chatnail service to require valid dkim is to prevent impersonation attacks.

Are you using a personal email server or a server with many users ?

Thanks for clarification.
The Email Server of my provider does not (yet?) support DKIM.
Using was only for testing purposes.

Delta Chat itself does not do any DKIM checks, it delegates doing all the checks and filtering spam to the email server.

chatmail servers such as reject all messages without a valid DKIM signature. Currently they also check DMARC policy but we are going to remove this check because the strictest DMARC policy requires either SPF or DKIM to pass, so it is redundant.

There are studies that show that as of 2022 many hosts also don’t support SPF:
Of top 1 million Alexa domain dataset 748,993 had MX records. Of these 69.8% support SPF and 37.0% support DKIM.
This does not tell much about email providers though because many of these hosts only send password reset emails. Large email providers such as Gmail, Fastmail etc. all have DKIM.

With this strict DKIM requirement on and clear error messages there is also a hope that Delta Chat users will switch to email providers that support DKIM, ask their email provider to fix the problem or provider will notice the problem from the server logs and fix it. It is always possible to setup a second chatmail account and use it for chatting with chatmail users if fixing own provider is difficult.

Holger, I raised an issue with my mail provider regarding the invalid DKIM signature error. They investigated and determined that their DKIM signatures are valid. Can you please take a look at what’s going on from your vantage point?

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Could you also test against (it runs OpenDKIM instead of rspamd) and (just need to send a mail to them and see the result)?

I PM’d you my address so you can also send me a mail, I will try to debug it then.

Test messages sent, thank you.