You can send emails to the group by posting a message from the web interface. http://www.groups.google.com/support/bin/topic.py?hl=en&topic=9253
Sending email to a Google@UH group from an email client is not supported at this time. If attempt to email the group via the email address, you will receive the following error:
Technical details of permanent failure:
Google tried to deliver your message, but it was rejected by the recipient domain. We recommend contacting the other email provider for further information about the cause of this error. The error that the other server returned was: 550 550 5.1.1 unknown or illegal alias: firstname.lastname@example.org (state 14).