From 8ff8b541ad67e88b3b17e6c43604e180a29765dd Mon Sep 17 00:00:00 2001
From: Alexander Vershilov <alexander.vershilov@sirius.online>
Date: Tue, 23 Nov 2021 18:06:23 +0300
Subject: [PATCH] Ignore 502 error on helo - fixes communication with some
 servers

Fixes #31.
---
 src/Network/HaskellNet/SMTP/SSL.hs | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/src/Network/HaskellNet/SMTP/SSL.hs b/src/Network/HaskellNet/SMTP/SSL.hs
index b3dd3ba..2ed35de 100644
--- a/src/Network/HaskellNet/SMTP/SSL.hs
+++ b/src/Network/HaskellNet/SMTP/SSL.hs
@@ -52,7 +52,7 @@ connectSTARTTLS hostname cfg = do
 
     hn <- getHostName
     bsPut bs $ B.pack ("HELO " ++ hn ++ "\r\n")
-    getResponse bs >>= failIfNot bs 250
+    getResponse bs >>= failIfNotEx bs (`elem` [250, 502])
     bsPut bs $ B.pack ("EHLO " ++ hn ++ "\r\n")
     getResponse bs >>= failIfNot bs 250
     bsPut bs $ B.pack "STARTTLS\r\n"
@@ -73,6 +73,11 @@ failIfNot :: BSStream -> Integer -> (Integer, String) -> IO ()
 failIfNot bs code (rc, rs) = when (code /= rc) closeAndFail
   where closeAndFail = bsClose bs >> fail ("cannot connect to server: " ++ rs)
 
+-- | Extended version of fail if, can support multiple statuses
+failIfNotEx :: BSStream -> (Integer -> Bool) -> (Integer, String) -> IO ()
+failIfNotEx bs f (rc, rs) = unless (f rc) closeAndFail
+  where closeAndFail = bsClose bs >> fail ("cannot connect to server: " ++ rs)
+
 -- This is a bit of a nasty hack.  Network.HaskellNet.SMTP.connectStream
 -- expects to receive a status 220 from the server as soon as it connects,
 -- but we've intercepted it in order to establish a STARTTLS connection.