let CheckHost email =
    let addr = new System.Net.Mail.MailAddress(email)
    let res = ActiveUp.Net.Mail.Validator.GetMxRecords(addr.Host)
    if res <> null then Some(res) else None

[<EntryPoint>]
let main argv =
    let emailValidator = (new System.ComponentModel.DataAnnotations.EmailAddressAttribute()).IsValid
    let validEmails = System.IO.File.ReadAllLines(argv.[0]) |> Seq.filter emailValidator
    System.IO.File.WriteAllLines(argv.[0] + "_out.txt", validEmails)
    let checkedEmails = validEmails |> Seq.map (fun e -> match CheckHost e with |Some res -> (e, res.Count) | None -> (e, 0))
    let badCount = checkedEmails |> Seq.filter (fun (e,c) -> c = 0) |> Seq.length
    printfn "%d bad emails" badCount
    System.IO.File.WriteAllLines(argv.[0] + "_out2.txt", validEmails)
    printfn "%f bad emails" (float(badCount) / float(Seq.length checkedEmails))
    System.Console.ReadLine() |> ignore
    0 // return an integer exit codes