Refactoring

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

@@ -731,6 +731,16 @@ public class MessageHelper {
         return TextUtils.join(", ", formatted);
     }
 
+    static String canonicalAddress(String address) {
+        String[] a = address.split("@");
+        if (a.length > 0) {
+            String[] extra = a[0].split("\\+");
+            if (extra.length > 0)
+                a[0] = extra[0];
+        }
+        return TextUtils.join("@", a).toLowerCase();
+    }
+
     static String decodeMime(String text) {
         if (text == null)
             return null;