Refactoring

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

@@ -460,6 +460,31 @@ public class MessageHelper {
         return (header == null ? null : header.replaceAll("\\r?\\n", ""));
     }
 
+    static Boolean getAuthentication(String type, String header) {
+        if (header == null)
+            return null;
+
+        // https://tools.ietf.org/html/rfc7601
+        Boolean result = null;
+        String[] part = header.split(";");
+        for (int i = 1; i < part.length; i++) {
+            String[] kv = part[i].split("=");
+            if (kv.length > 1) {
+                String key = kv[0].trim();
+                String[] val = kv[1].trim().split(" ");
+                if (val.length > 0 && type.equals(key)) {
+                    if ("fail".equals(val[0]))
+                        result = false;
+                    else if ("pass".equals(val[0]))
+                        if (result == null)
+                            result = true;
+                }
+            }
+        }
+
+        return result;
+    }
+
     Address getSender() throws MessagingException {
         String sender = imessage.getHeader("Sender", null);
         if (sender == null)