We have an application running passwordless authentication. For a number of reasons, our emails are often being left as spam in customer’s mailboxes. After contact with an email provider they agreed to give us a list of rspamd rules our messages had breached, one of the most significant, R_MISSING_CHARSET is triggered when an encoding isn’t specified in the content-type header.
Just to be completely sure, is it Auth0 that crafts these headers when it sends the mail? And if so, could you add this to the headers?
You can see the rules here. rspamd/headers.lua at 373090429416571046f333c1f68707bb752e562d · rspamd/rspamd · GitHub
While the rule appears to be only affecting text/plain segments, I’ve noticed previous versions match all text types, so it may be best if all segments set character encoding. From what I’ve seen the meta tag that is set in the default email template html won’t be read.