> On 21 Oct 2024, at 14:28, Florian Effenberger via mailop <mailop@mailop.org> > wrote: > > Hello, > > Florian Effenberger via mailop wrote on 21.10.24 at 10:33: >> I just sent an e-mail to the affected domain, Bcc my GMail address. For that >> very mail, GMail confirms the DKIM signature is proper, whereas Mimecast >> bounces it. >> The only two options left are that Mimecast has hiccups with my DNS setup >> (which would be strange, as all major providers work flawless with it, and >> they seem to be able to load the SPF records from that very DNS), or >> stumbles over something else in my rspamd configuration (which would be >> strange as well, because that is pretty much a standard setup). > > thanks to a friendly reader of this list, I tested the mail also with > aboutmy.email. > > I can confirm now that when the Content-Encoding is 8bit, it gets bounced by > Mimecast, and also flagged as erroneus by aboutmy.email. When I switch to > Quote-Printable, the mail passes both just fine. > > As I consider my setup pretty standard, and I don't modify the e-mail, I > wonder if this is a bug in rspamd, in Mimecast, or in the > connection of these two…
So I believe (and I’m sure that one of the experts here will correct me when I get it wrong), in order to send UTF8 the receiving server needs to advertise it will accept 8BITMIME. Mimecast does not advertise that: nc service-alpha-inbound-a.mimecast.com 25 220 eu-smtp-inbound-1.mimecast.com ESMTP; Mon, 21 Oct 2024 15:10:30 +0100 EHLO wordtothewise.com 250-eu-smtp-inbound-1.mimecast.com Hello [104.225.223.158] 250-STARTTLS 250 HELP quit Google does advertise that: nc smtp.google.com 25 220 mx.google.com ESMTP 5614622812f47-3e6102ab430si1715351b6e.119 - gsmtp EHLO wordtothewise.com 250-mx.google.com at your service, [104.225.223.158] 250-SIZE 157286400 250-8BITMIME 250-STARTTLS 250-ENHANCEDSTATUSCODES 250-PIPELINING 250-CHUNKING 250 SMTPUTF8 quit So the issue might be that you’re attempting to send 8 bit mime to a service that doesn’t support it. So it might not be rspamd that’s the problem here, but rather your instance of postfix isn’t handling ESMTP correctly. laura -- The Delivery Expert Laura Atkins Word to the Wise la...@wordtothewise.com Delivery hints and commentary: http://wordtothewise.com/blog
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