>> What kind of software is that on 127.0.0.1:10025? It's neither amavis nor >> postfix. > > Crap I missed that! it's James Java SMTP for Ciphermail.
If you cannot enable 8BITMIME support on it, you might try to discard the 8BITMIME ehlo keyword on the 10021 amavis instance/policybank. This way, your postfix:25 should convert to 7BIT before feeding the mail into amavis:10021. This is also mentioned in [1] with its caveats. [1] https://www.ijs.si/software/amavisd/amavisd-new-docs.html
