X-Git-Url: http://gitweb.michael.orlitzky.com/?a=blobdiff_plain;f=src%2FMain.hs;h=74789e70f4e2cedbf0be6584c3b14626046bed52;hb=432089f7b63e96b6e15ad7895f0e4b6aa1a52efc;hp=1cc4c73aa47d963e56f30a7188f05781f010b76c;hpb=2e8aab2a69a8b9887e4f037115b80a2063d3a6b7;p=email-validator.git

diff --git a/src/Main.hs b/src/Main.hs
index 1cc4c73..74789e7 100644
--- a/src/Main.hs
+++ b/src/Main.hs
@@ -41,25 +41,58 @@ import EmailAddress(
 resolv_conf ::  ResolvConf
 resolv_conf = defaultResolvConf { resolvTimeout = 10 * 1000 * 1000 }
 
--- | A list of common domains, there's no need to waste MX lookups
---   on these.
+-- | A list of common domains, there's no need to waste MX lookups on
+--   these. This is a very limited list; I don't want to be in the
+--   business of monitoring a million domains for MX record updates.
 common_domains :: [Domain]
 common_domains = map BS.pack [ "aol.com",
                                "comcast.net",
+                               "cox.net",
                                "gmail.com",
+                               "gmx.de",
+                               "googlemail.com",
+                               "hotmail.com",
+                               "icloud.com",
+                               "live.com",
+                               "me.com",
                                "msn.com",
+                               "outlook.com",
+                               "proton.me",
+                               "protonmail.ch",
+                               "protonmail.com",
                                "yahoo.com",
                                "verizon.net" ]
 
 
--- | Check whether the given domain has a valid MX record.
+-- | Check whether the given domain has a valid MX record. NULLMX
+--   (RFC7505) records consisting of a single period must not be
+--   accepted.
+--
+--   Two points about NULLMX:
+--
+--   * RFC7505 states that a domain MUST NOT have any other MX records
+--   if it has a NULLMX record. We don't enforce this. If you have a
+--   NULLMX record and some other MX record, we will reluctantly
+--   consider the second one valid.
+--
+--   * RFC7505 also states that a NULLMX record must have a priority
+--   of 0. We do not enforce this either. We ignore any records
+--   containing an empty label (i.e. a single dot). Such a record will
+--   not be deliverable anyway, and in light of the first item, means
+--   that we will not \"incorrectly\" reject batshit-crazy domains
+--   that have a NULLMX record (but with a non-zero priority) in
+--   addition to other, valid MX records.
+--
+
 validate_mx :: Resolver -> Domain -> IO Bool
 validate_mx resolver domain
   | domain `elem` common_domains = return True
   | otherwise = do
       result <- lookupMX resolver domain
-      case result of
-        -- A list of one or more elements?
+      let nullmx = BS.pack "." :: Domain
+      let non_null = (\(mx,_) -> mx /= nullmx) :: (Domain,Int) -> Bool
+      let non_null_mxs = fmap (filter non_null) result
+      case non_null_mxs of
         Right (_:_) -> return True
         _           -> return False