5. At least guidelines of [Debian mailing lists](http://www.debian.org/MailingLists/#codeofconduct), [Ubuntu mailing lists](http://www.ubuntu.com/support/community/mailinglists) and [Linux Kernel Developer mailing lists](http://vger.kernel.org/majordomo-info.html) forbid writing emails in HTML. Hopefully others do to, at least they should.
Are you sure? [Debian wiki](https://wiki.debian.org/DebianMailingLists#HowTo_send_plain_text_emails_to_the_list) has instructions how to write plain text with many clients.
But I use webmail, I cannot send plaintext!
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Are you sure? [Debian wiki, which was mentioned eaerier](https://wiki.debian.org/DebianMailingLists#HowTo_send_plain_text_emails_to_the_list) also includes instructions for many webmails about writing in plaintext.