gmail + imap - hangs when sending

[Paul Mead]

Hi, I hope someone can help, I've been Googling but can't find any help.

When I try to send a message via IMAP / Gmail, it appears to send but
emacs hangs. Eventually I use C-g to exit and find the following in *Messages*:

Sending...
Sending via mail...
Opening STARTTLS connection to `smtp.gmail.com'...done
221 2.0.0 closing connection d25sm194468nfh.36

Nothing is actually sent as far as I can tell (at least, nothing is
received and there are no items in 'Sent items')

The relevant bits of configuration are:

(setq starttls-use-gntls t)

(setq send-mail-function 'smtpmail-send-it
      message-send-mail-function 'smtpmail-send-it
      smtpmail-starttls-credentials
      '(("smtp.gmail.com" 587 nil nil))
      smtpmail-auth-credentials
      (expand-file-name "~/.authinfo")
      smtpmail-default-smtp-server "smtp.gmail.com"
      smtpmail-smtp-server "smtp.gmail.com"
      smtpmail-smtp-service 587
      smtpmail-debug-info t)

I am using cygwin on Vista and emacs 22.3 for Windows. Not sure how to
check which gnus version...

Does anyone have a solution for this?

Thanks, Paul