LMTP is broken on director:

Jul 13 13:42:41 lmtp(34824): Panic: file smtp-params.c: line 685 (smtp_params_mail_add_body_to_event): assertion failed: ((caps & SMTP_CAPABILITY_8BITMIME) != 0)

Thanks, fixed: https://github.com/dovecot/core/commit/c4de81077c11d09eddf6a5c93676ee82350343a6