Answer by S.R for Sending Email in Android using JavaMail API without using the default/built-in app

GmailBackground is small library to send an email in background without user interaction :

Usage:

    BackgroundMail.newBuilder(this)            .withUsername("username@gmail.com")            .withPassword("password12345")            .withMailto("toemail@gmail.com")            .withType(BackgroundMail.TYPE_PLAIN)            .withSubject("this is the subject")            .withBody("this is the body")            .withOnSuccessCallback(new BackgroundMail.OnSuccessCallback() {                @Override                public void onSuccess() {                    //do some magic                }            })            .withOnFailCallback(new BackgroundMail.OnFailCallback() {                @Override                public void onFail() {                    //do some magic                }            })            .send();

Configuration:

repositories {    // ...    maven { url "https://jitpack.io" } } dependencies {            compile 'com.github.yesidlazaro:GmailBackground:1.2.0'    }

Permissions:

<uses-permission android:name="android.permission.ACCESS_NETWORK_STATE"/><uses-permission android:name="android.permission.INTERNET"/>

Also for attachments, you need to set READ_EXTERNAL_STORAGE permission:

<uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE"/>

Source

(I've tested it myself)