Prevent new message notifications on first sync

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

@@ -71,6 +71,7 @@ import java.text.Collator;
 import java.util.ArrayList;
 import java.util.Collections;
 import java.util.Comparator;
+import java.util.Date;
 import java.util.List;
 import java.util.Locale;
 import java.util.Properties;
@@ -682,6 +683,9 @@ public class FragmentAccount extends FragmentEx {
                             account.primary = (account.synchronize && primary);
                             account.poll_interval = Integer.parseInt(interval);
 
+                            if (!update)
+                                account.seen_until = new Date().getTime();
+
                             account.store_sent = false;
 
                             if (!synchronize)