I'm using web based outlook 2013 and I want to change the content-type form 'multipart/alternative' to 'text/plain' because some mailing list forbid the first choice.
fatal: Sorry, I don't accept messages of MIME Content-Type 'multipart/alternative' (#5.2.3). Sorry, for security reasons this list only accepts plain text email and no large attachments. Please configure your mail client accordingly
So, any ideas about how to change the content-type?