We want SocialCaddy to send HTML emails with daily digests to our users. Well there is nothing fancy about it but we spent one day trying to do that on Google App Engine.

We use the Python framework web2py. After digging with the web2py source code we found a tiny bug that prevented us from sending HTML emails from App Engine. If you face a similar problem then just go to gluon/tools.py and replace line 437 with the following code:

result = mail.send_mail(sender=self.settings.sender, to=to, subject=subject, body=text, html=html)

We hope that no one else will spend 5 hours on such a tiny bug :)