Apologize for the commercial message - but this one shows a weird effect
in the html display for me. This is with GNU Emacs 23.1.94.1
(x86_64-redhat-linux-gnu, GTK+ Version 2.19.7) under X running the
latest notmuch.

When displaying this as html I see 

[4]View as a Web
page  |  [5]Español      Ensure
delivery to your inbox.

(let's see how that transports... "Web page\302\240\302\249...")

/D