Try secondary ip4 addresses first when ip4 preferred

app/src/main/java/eu/faircode/email/EmailService.java

@@ -67,6 +67,7 @@ import java.security.cert.X509Certificate;
 import java.util.ArrayList;
 import java.util.Arrays;
 import java.util.Collections;
+import java.util.Comparator;
 import java.util.Date;
 import java.util.HashMap;
 import java.util.LinkedHashMap;
@@ -617,6 +618,8 @@ public class EmailService implements AutoCloseable {
         crumb.put("port", Integer.toString(port));
         crumb.put("auth", Integer.toString(auth));
 
+        SharedPreferences prefs = PreferenceManager.getDefaultSharedPreferences(context);
+
         InetAddress main = null;
         boolean require_id = (purpose == PURPOSE_CHECK &&
                 auth == AUTH_TYPE_OAUTH &&
@@ -627,8 +630,6 @@ public class EmailService implements AutoCloseable {
             //    throw new MailConnectException(
             //            new SocketConnectException("Debug", new IOException("Test"), host, port, 0));
 
-            SharedPreferences prefs = PreferenceManager.getDefaultSharedPreferences(context);
-
             String key = "dns." + host;
             try {
                 main = DnsHelper.getByName(context, host, dnssec);
@@ -748,6 +749,15 @@ public class EmailService implements AutoCloseable {
                             " ip4=" + ip4 + " max4=" + MAX_IPV4 + " has4=" + has46[0] +
                             " ip6=" + ip6 + " max6=" + MAX_IPV6 + " has6=" + has46[1]);
 
+                    boolean prefer_ip4 = prefs.getBoolean("prefer_ip4", true);
+                    if (prefer_ip4)
+                        Arrays.sort(iaddrs, new Comparator<InetAddress>() {
+                            @Override
+                            public int compare(InetAddress a1, InetAddress a2) {
+                                return -Boolean.compare(a1 instanceof Inet4Address, a2 instanceof Inet4Address);
+                            }
+                        });
+
                     for (InetAddress iaddr : iaddrs) {
                         EntityLog.log(context, EntityLog.Type.Network, "Address resolved=" + iaddr);