Without user intervention, you can send as follows:
Send email from client apk. Here mail.jar, activation.jar is required to send java email. If these jars are added, it might increase the APK Size.
Alternatively, You can use a web-service at the server side code, which will use the same mail.jar and activation.jar to send email. You can call the web-service via asynctask and send email. Refer same link.
(But, you will need to know the credentials of the mail account)