The identity used to send the announcement mail can be customized. It can be either a member of the <developers> section of the POM or it can be specified explicitly with the <mailSender> parameter of the plugin.
To specify which developer is used to send the announcement, simply specify the id of the developer as in the example below:
<project>
  <developers>
    ...
    <developer>
      <id>jsmith</id>
      <name>John Smith</name>
      <email>jsmith@foo.bar</email>
    </developer>
    ...
  </developers>
  ...
  <build>
    <plugins>
      <plugin>
        <groupId>org.apache.maven.plugins</groupId>
        <artifactId>maven-changes-plugin</artifactId>
        <version>2.7.1</version>
        <configuration>
          <fromDeveloperId>jsmith</fromDeveloperId>
        </configuration>
      </plugin>
    </plugins>
  </build>
  ...
</project>If no developer id is specified, the first <developer> in the list will be used.
You can also do this from the command line, if the person doing the release changes between releases.
mvn -Dchanges.fromDeveloperId=jsmith changes:announcement-mail
If you want to specify the sender explicitly and not rely on the developers section of your POM, define the mailSender parameter of the plugin.
<project>
  ...
  <build>
    <plugins>
      <plugin>
        <groupId>org.apache.maven.plugins</groupId>
        <artifactId>maven-changes-plugin</artifactId>
        <version>2.7.1</version>
        <configuration>
          <mailSender>
            <name>Release Notification</name>
            <email>noreply@foo.bar</email>
          </mailSender>
        </configuration>
      </plugin>
    </plugins>
  </build>
  ...
</project>