我需要刷新SMTP服务器吗？如果是，该怎么办？

cabal install SMTPClient

import Network.SMTP.ClientSession
import Network.SMTP.Client
import Network.Socket
import System.Time
import System.IO
import Data.Bits
import Data.IORef

myDomain = \"example.com\"
smtpHost = \"hubert.blacksapphire.com\"    -- <-- Your SMTP server here

-- This will send the author an email.  I don\'t mind!
main = do
    now <- getClockTime
    nowCT <- toCalendarTime now
    let message = Message [
                From [NameAddr (Just \"Mr. Nobody\") \"nobody@example.com\"],
                To   [NameAddr (Just \"Stephen Blackheath\") \"unprintable.distances.stephen@blacksapphire.com\"],
                Subject \"I\'m using SMTPClient!\",
                Date nowCT
            ]
            (\"Dear Sir,\\n\"++
             \"It has come to my attention that this is an email.\\n\"++
             \"Yours sincerely,\\n\"++
             \"Mr. Nobody\\n\")
    addrs <- getAddrInfo Nothing (Just smtpHost) Nothing
    let SockAddrInet _ hostAddr = addrAddress (addrs !! 0)
        sockAddr = SockAddrInet (fromIntegral 25) hostAddr
    putStrLn $ \"connecting to \"++show sockAddr
    sentRef <- newIORef []
    sendSMTP\' (hPutStrLn stderr) (Just sentRef) myDomain
        sockAddr [message]
    statuses <- readIORef sentRef
    -- If no exception was caught, statuses is guaranteed to be
    -- the same length as the list of input messages, therefore head won\'t fail here.
    case head statuses of
        Nothing     -> putStrLn \"Message successfully sent\"
        Just status -> putStrLn $ \"Message send failed with status \"++show status