diff -r ef52758f69c6 libs/amavisd/__init__.py
--- a/libs/amavisd/__init__.py    Fri Feb 20 13:15:06 2015 +0800
+++ b/libs/amavisd/__init__.py    Wed Feb 25 11:49:38 2015 +0800
@@ -28,13 +28,14 @@
 #   1 - lookup for @.com
 #   0 - lookup for @.       (catchall)
 MAILADDR_PRIORITIES = {
+    'ip': 10,
     'email': 8,
     'wildcard_addr': 6,     # r'user@*'. used in iRedAPD plugin `amavisd_wblist`
                             # as wildcard sender. e.g. 'user@*'
     'domain': 5,
     'subdomain': 3,
+    'top_level_domain': 1,
     'catchall': 0,
-    'ip': 10,
 }
 
 
@@ -52,13 +53,14 @@
     #          a new address format.
     if addr.startswith(r'@.'):
         if addr == r'@.':
-            # catch all
             return 'catchall'
         else:
-            # sub-domain
             domain = addr.split(r'@.', 1)[-1]
+
             if iredutils.is_domain(domain):
                 return 'subdomain'
+            elif iredutils.is_tld_domain(domain):
+                return 'top_level_domain'
 
     elif addr.startswith(r'@'):
         # entire domain
diff -r ef52758f69c6 libs/iredutils.py
--- a/libs/iredutils.py    Fri Feb 20 13:15:06 2015 +0800
+++ b/libs/iredutils.py    Wed Feb 25 11:49:38 2015 +0800
@@ -19,7 +19,8 @@
 regx_email = r'''[\w\-][\w\-\.\+\=]*@[\w\-][\w\-\.]*\.[a-zA-Z0-9\-]{2,15}'''
 
 # Domain name
-regx_domain = r'''[\w\-][\w\-\.]*\.[a-z0-9\-]{2,15}'''
+regx_domain = r'''[\w\-][\w\-\.]*\.[a-z0-9\-]{2,25}'''
+regx_top_level_domain = r'''[a-z0-9\-]{2,25}'''
 
 # IP address
 regx_ipv4 = r'(?:[\d]{1,3})\.(?:[\d]{1,3})\.(?:[\d]{1,3})\.(?:[\d]{1,3})$'
@@ -56,6 +57,16 @@
         return False
 
 
+def is_tld_domain(s):
+    s = str(s)
+
+    comp_domain = re.compile(regx_top_level_domain + '$', re.IGNORECASE)
+    if comp_domain.match(s):
+        return True
+    else:
+        return False
+
+
 # Valid IP address
 def is_ipv4(s):
     if re.match(regx_ipv4, s):