Question

I am on GAE Version 1.7.3 and using java mail api to send the email. On local development server the mail is sent fine. But after deploying to app engine i get following exception

com.google.apphosting.api.ApiProxy$CallNotFoundException: The API package 'remote_socket' or call 'Resolve()' was not found.
    at java.lang.Thread.getStackTrace(Thread.java:1495)
    at com.google.apphosting.runtime.ApiProxyImpl.doSyncCall(ApiProxyImpl.java:240)
    at com.google.apphosting.runtime.ApiProxyImpl.access$000(ApiProxyImpl.java:66)
    at com.google.apphosting.runtime.ApiProxyImpl$1.run(ApiProxyImpl.java:183)
    at com.google.apphosting.runtime.ApiProxyImpl$1.run(ApiProxyImpl.java:180)

    at java.security.AccessController.doPrivileged(Native Method)

    at com.google.apphosting.runtime.ApiProxyImpl.makeSyncCall(ApiProxyImpl.java:180)

    at com.google.apphosting.runtime.ApiProxyImpl.makeSyncCall(ApiProxyImpl.java:66)

    at com.google.apphosting.api.ApiProxy.makeSyncCall(ApiProxy.java:107)
    at com.google.apphosting.api.ApiProxy.makeSyncCall(ApiProxy.java:56)

    at com.google.appengine.api.socket.SocketApiHelper.apiProxyMakeSyncCall(SocketApiHelper.java:90)

    at com.google.appengine.api.socket.SocketApiHelper.makeSyncCall(SocketApiHelper.java:58)

    at com.google.appengine.api.socket.NameServiceImpl.lookupAllHostAddr(NameServiceImpl.java:61)

    at com.google.apphosting.util.ResolverManager$AppEngineNameservice.lookupAllHostAddr(ResolverManager.java:42)

    at java.net.InetAddress.getAddressFromNameService(InetAddress.java:1353)
    at java.net.InetAddress.getAllByName0(InetAddress.java:1303)

    at java.net.InetAddress.getAllByName(InetAddress.java:1232)

    at java.net.InetAddress.getAllByName(InetAddress.java:1163)

    at java.net.InetAddress.getByName(InetAddress.java:1113)

    at javax.mail.Service.connect(Service.java:257)

    at javax.mail.Service.connect(Service.java:91)

    at javax.mail.Service.connect(Service.java:76)

    at javax.mail.Transport.send(Transport.java:94)
    at javax.mail.Transport.send(Transport.java:48)
    at com.test.igreetings.service.impl.EmailImpl.sendEmail(EmailImpl.java:61)

Here is the my code to send the email:

try {
            // Email is my custom pojo class
            Email email = new Email();
            email.setMailHost("smtp.gmail.com");
            email.setAuth("true");
            email.setFrom("[e-mail]");
            email.setTo("[e-mail]");
            email.setSubject("test);
            email.setMessage("test body");
            email.setPort("25");
            email.setStarttls("true");
            email.setLogin("[e-mail]");
            email.setPassword("pwd");

            Properties props = new Properties();
            props.setProperty("mail.host", email.getMailHost());
            props.setProperty("mail.smtp.port", email.getPort());
            props.setProperty("mail.smtp.auth", email.getAuth());
            props.setProperty("mail.smtp.starttls.enable", email.getStarttls());

            Authenticator auth = new SMTPAuthenticator(email.getLogin(), email.getPassword());

            Session session = Session.getInstance(props, auth);

            MimeMessage msg = new MimeMessage(session);
            msg.setText(email.getMessage());
            msg.setSubject(email.getSubject());
            msg.setFrom(new InternetAddress(email.getFrom()));
            msg.addRecipient(Message.RecipientType.TO, new InternetAddress(email.getTo()));
            Transport transport = session.getTransport("smtp");
            transport.connect(email.getMailHost(), 25, "[e-mail]", "pwd");

            transport.sendMessage(msg, msg.getAllRecipients());

            transport.close();
        } catch (AuthenticationFailedException ex) {
            Logging.log("AuthenticationFailedException in sendEmail: " + ex.toString());
            ex.printStackTrace();

        } catch (AddressException ex) {

            Logging.log("AddressException in sendEmail: " + ex.toString());
            ex.printStackTrace();
        } catch (MessagingException ex) {
            Logging.log("MessagingException in sendEmail: " + ex.toString());
            ex.printStackTrace();
        }

EDIT:

I have changed code per your suggestion and here is my updated code:

Properties props = new Properties();
                        Session session = Session.getDefaultInstance(props, null);
                        Message msg = new MimeMessage(session);
                        msg.setFrom(new InternetAddress("[e-mail]"));
                        msg.addRecipient(Message.RecipientType.TO,
                        new InternetAddress("[e-mail]"));
                        msg.setSubject("test");
                        msg.setText("test");
                        Transport.send(msg);

And i am getting similar exception The API package ‘remote_socket’ or call ‘CreateSocket()’ was not found. The above sender is also registered as developer of this application.

Answer 1

As @Shay noted you can not use external SMTP provider with GAE. GAE uses it’s own SMTP gateway.

Related issue: on GAE you can only send email that originates (i.e. from field) from one of the app administrators (GAE Admin -> permissions) or currently logged-in users via Google Accounts. Note: this only works for users logged-in via Google Accounts, not for users logged in via federated login (e.g. OpenID): Sending email on behalf of Google Apps user (answer is from Google engineer)

Update: as noted before, the [e-mail] must be the email of the user that logged into your GAE app via Google Apps login or the user must be an admin of your GAE app.

Update2: this works for me:

Properties props = new Properties();
Session session = Session.getDefaultInstance(props, null);
try {
    Message msg = new MimeMessage(session);
    msg.setFrom(new InternetAddress("[e-mail]", "Admin", "UTF-8"));
    msg.addRecipient(Message.RecipientType.TO, new InternetAddress(recipientAddress));
    msg.setSubject(emailSubject);
    msg.setText(emailText);
    Transport.send(msg);

} catch (AddressException e) {
// TO address not valid
} catch (MessagingException e) {
    // other email error
} catch (UnsupportedEncodingException e) {
    // should not happen UTF-8 is always available
}