How to disable or fix the wysiwyg editor on civimail
Editing markup

The editor includes a "Source" button which can be used to edit markup directly.

Using &lt;textarea&gt;

Upgrade to v4.7!

In depth

CiviCRM v4.6 includes a pure-JS rewrite of the CiviMail frontend. Unfortunately, the old WYSIWYG abstraction couldn't adapt well to pure-JS, so CiviMail in v4.6 only supports one editor. (Specifically, CiviMail uses the crmUiRichtext directive which is hardcoded to CKEditor.) However, all other screens still use the old WYSIWYG abstraction.

v4.7 cleans things up by switching to a pure-JS WYSIWYG abstraction. The core ships with only two options (CKEditor and &lt;textarea&gt;). However, you can write an extension that defines alternatives (e.g. https://civicrm.org/extensions/tinymce ).

See also: https://civicrm.org/blogs/colemanw/big-changes-wysiwyg-editing-47