gnus cannot send emails using smtp with starttls (i.e. gmail)

This is also reported upstream: http://tracker.xemacs.org/XEmacs/its/issue788

The problem is actually that the function smtpmail-open-stream uses a
macro `with-boundp' that is not defined in 21.4.22, but only in 21.5
(http://membled.com/lib/xemacs-21.5-b27/lisp/bytecomp-runtime.el)

Others have run into this problem:
http://groups.google.com/group/gnu.emacs.help/browse_thread/thread/2538363186504a06/ba2a2effcce72898

Therefore the OS process is never created and an internal network stream
is created instead.

There is a workaround:
1) Put the definition of `with-boundp' in the .gnus file.
2) Disable the bytecompiled smtpmail or redefnie `smtpmail-open-stream'
in your .gnus after it has been loaded from you OS distibuted version.

That will fix it.