On Friday 15 Mar 2013 17:36:48 Kevin Chadwick wrote:

From the headers of his email:

Subject: Re: [gentoo-user] Gentoo speed comparison to other distros
References: <51418728.7020406@gmail.com>
In-Reply-To: <51418728.7020406@gmail.com>
Content-Type: text/html; charset=ISO-8859-1
Content-Transfer-Encoding: 7bit

It's perfectly compliant. You may want to correct your mail client to
understand HTML.

(Admittedly, it's unusual to see email clients send *only* text/html,
rather than a multipart message with two different encodings.)

ROFL. It's called "me wrestling with thunderbird to try to remove html
formatting but failing".

Compulsory html annoys me on Android (If only you could have proper
programs like Nokias N9 had claws)

Claws would mean you needn't bother and still have html to text by
default and can even enable html plugins if desired (right way around).

I understand that you can specify what sort of mail format you want to send 
per email recipient, including of course <gentoo-user@lists.gentoo.org>, but I 
don't have T'bird installed to check:

  http://kb.mozillazine.org/Plain_text_e-mail_(Thunderbird)

HTH.