Google Apps reduce IT costs and empower today’s employees. Gmail, Google Docs, Google Sites, and more. Using the email service under the Google Apps architecture is still the same. You can remotely use the SMTP server of Gmail to send emails using the address smtp.gmail.com.
If say, you are using JavaMail to send emails via Gmail’s smtp server, no code change is necessary. I thought at first, while reading the Google Apps documentation that you need to upload your application and/or web application to Google’s server in order for you to be able to send emails under the Google Apps Engine but this does not seem to be the case since I successfully sent a test email remotely.