The e-mail backends allow you to use native Django functions for sending e-mails like django.core.mail.send_mail() on App Engine.
To use pluggable e-mail backends you'll have to use a recent version of Django. Support for pluggable e-mail backends was introduced in rev11709 and will be released in Django 1.2.
Using the e-mail backend
The e-mail backends are available as a single package on bitbucket. To check out the most recent sources run:
$ hg clone http://bitbucket.org/andialbrecht/appengine_emailbackends/
To use the e-mail backend for App Engine copy the appengine_emailbackend directory to the top-level directory of you App Engine application and add the following line to your settings.py:
EMAIL_BACKEND = 'appengine_emailbackend'
If you prefer asynchronous e-mail delivery use this line in your settings.py instead:
EMAIL_BACKEND = 'appengine_emailbackend.async'
When using the async backend e-mails will not be sent immediately but delivered via a taskqueue.
Running the demo application
There's also a demo application included in this repository. Run this application using
$ dev_appserver.py .
and open http://localhost:8080 in your web browser. Remember to include a current checkout of the Django SVN repository in the top-level directory of the demo application.