[Rspamd-Users] rspamd DKIM, Mimecast and Content-Encoding

Florian Effenberger florian at effenberger.org
Mon Oct 21 19:36:23 UTC 2024


Hello everyone,

let me thank you again for helping me out with this issue, I am really 
glad to see so much discussion and support here!

I started that discussion at Mailop, and now indeed thanks to the 
feedback from this list and the Mailop list, I get an understanding of 
the problem. It is not a rspamd bug I'd say.

Both Mimecast as well as aboutmy.email do not announce 8BITMIME, while 
other sites for testing like dmarctester or dkimvalidator support it. I 
just checked that for all these MX.

That seems to explain why the signature works correctly for nearly 
everywhere, except for these two sites (and I actually appreciate 
aboutmy.email's settings, because that helped to identify the problem!).

I was briefly confused with SMTPUTF8, but the issue is actually 8BITMIME.

So, my client sends with 8BITMIME, rspamd signs, and when delivering to 
a non-8BITMIME enabled site, the signature breaks. That means I need to 
do a conversion before, when sending to these sites at least.

Newer Postfix versions support force_mime_input_conversion, which seem 
to do the job.

Thanks everyone!
Florian


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