Small improvement

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

@@ -1337,7 +1337,7 @@ public class EmailService implements AutoCloseable {
                 " reuse=" + reuse +
                 " delay=" + delay);
 
-        if (keepAlive || BuildConfig.DEBUG) {
+        if (keepAlive) {
             Log.e("Socket keep-alive=" + keepAlive);
             socket.setKeepAlive(false); // sets SOL_SOCKET/SO_KEEPALIVE
         }

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

@@ -286,7 +286,10 @@ public class FragmentOptionsConnection extends FragmentBase implements SharedPre
             @Override
             public void onCheckedChanged(CompoundButton compoundButton, boolean checked) {
                 try {
-                    System.setProperty("fairemail.tcp_keep_alive", Boolean.toString(checked));
+                    if (checked)
+                        System.setProperty("fairemail.tcp_keep_alive", Boolean.toString(checked));
+                    else
+                        System.clearProperty("fairemail.tcp_keep_alive");
                     prefs.edit().putBoolean("tcp_keep_alive", checked).apply();
                 } catch (Throwable ex) {
                     Log.e(ex);