When deleting text/html from the list of rejected mimetypes, emails with HTML attachments and/or alternative mime parts are still rejected.
See https://lists.sr.ht/~sircmpwn/sr.ht-discuss/%3Ce6e7c80d-0947-d9a5-d708-368e1e5d91d2%40protonmail.com%3E#%3C87ediqshyx.fsf@bzg.fr%3E for a related discussion.