Good catch on the DMARC policies, I forgot about the bounce-back messages. Gmail was indeed rejecting them bounced messages (see logs below).

Good news: your .forward if correctly configured, as I see your emails in the smtpd logs.
Bad news: You're facing a scribo(1) limitation that I forgot to mention… Here is the log entry (I removed your original email email):


The important part is "Content-Type: multipart/alternative; boundary="000000000000eecdd505afab7145" is not supported".

Currently, scribo(1) is not smart enough to parse multipart/* messages, and can only handle messages in text/plain. So you must ensure you're sending plain text email for now (patches welcome!).

That's definitely something that should be in the manpage.