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Figure 8-9. Email sent from the App Engine Mail service
In this section you viewed the features of App Engine's Mail service. You learned
that only deployed applications can use the Mail service. Once deployed, you can
send e-mails to individuals or larger distribution groups. Sometimes Mail isn't the
best option for communicating with your application's users. What if you had a
requirement for using instant messaging? Well, Google App Engine provides an XMPP
service in addition to the other services discussed in this chapter.
XMPP Service
The XMPP service works slightly differently from the Mail service in that users must
perform an action before you can send them a message. With the Mail API, you only
had to worry about valid “from” addresses. You could send a message to whomever
you wanted. With XMPP, users to whom you are going to send a message need to
add the App Engine application to their Google Talk friend list or their Jabber client
buddy list. In this example, you'll use Google Talk. If you don't have a Google Talk
account, you can register for a free account at
This example requires that you deploy this application to App Engine. The
XMPP service will not work from the local development server. This example
uses the App Engine application ID apressxmpp . If you recall from Chapter 3,
application IDs are unique across all App Engine applications. Once deployed,
your application gets its own domain name. In addition, the
applications also get a mapped handler in the form of an e-mail address, for
example, Before you can have your application send
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