App Engine Documentation PHP Standard Environment Documentation API Documentation \google\appengine\api\mail Classes AdminMessage Allows users to send mail to application admins using the App Engine mail APIs. BaseMessage Abstract base class for sending mail using the App Engine mail APIs. Message Allows users to send mail using the App Engine mail APIs. Except as otherwise noted, the content of this page is licensed under the Creative Commons Attribution 3.0 License, and code samples are licensed under the Apache 2.0 License. For details, see our Site Policies. Java is a registered trademark of Oracle and/or its affiliates. Last updated February 22, 2017.