Each night, our web server automatically sends out admin reports to certain company execs. These are in HTML form and typically involve a short inline CSS style block followed by a formatted table. All the execs are using a COS that has View as HTML (when possible) set by default.
Up through 5.0.4, the reports were displayed in formatted table form regardless of what tool the exec used to view them.
Immediately upon my upgrading to 5.0.5, however, one exec who uses the Zimbra Ajax web interface (using Firefox 22.214.171.124 on a Windows XP SP2 laptop) complained that the reports were being presented as plain text both in the Reading Pane and in a secondary window. A colleague of his, who receives email copies of the exact same reports, views his mail using Thunderbird via IMAP. He noticed no difference since the upgrade -- his reports continue to be displayed in formatted table form. When I stood over his shoulder and asked him to open his mailbox and view the same email instead using the Zimbra Ajax web interface, it was presented in plain text form only.
What could be going on? Neither of these guys has messed with his preferences so as to override the default COS settings, but the Zimbra Ajax web interface seems actually to be stripping the formatting HTML from the message -- the only vestige of HTML remaining being <br /> line breaks.