Failure sending mail (using Gmail Service) RSS

• • Reply
  kengkit

  Member

  103 Points

  793 Posts

  Failure sending mail (using Gmail Service)

  Feb 02, 2021 08:38 AM|kengkit|LINK

  Hi guys.. i getting this error while trying to send an email via smtp.gmail.com
  The SMTP server requires a secure connection or the client was not authenticated. The server response was: 5.7.0 Authentication Required. Learn more at
  
  The following is my code for sending emails out. sender@hello.com is a Google business email account.
  This web application is parked at www.byebye.com which let system user send an email out.
  
  Anything wrong to my code or setting?
  
  

      Public Function SendEmail() As Boolean
  
          Dim success As Boolean = False
  
          'Recipient email
          Dim [to] As String = "receiver@gmail.com"
          Dim cc As String = ""
          Dim bcc As String = ""
  
          'Sender email
          Dim from As String = "sender@hello.com"
  
          'Sender account
          Dim fromName As String = "HELLO WORLD"
          Dim userName As String = "sender@hello.com"
          Dim password As String = "fd##4jhAbWQ"
  
          Dim attachment As Attachment = Nothing
  
          Dim client As New SmtpClient()
          client.EnableSsl = "True"
  
          client.Credentials = New System.Net.NetworkCredential(userName, password)
          client.Port = "587"
          client.Host = "smtp.gmail.com"
  
          Try
              Using mail As New MailMessage()
                  mail.From = New MailAddress(from, fromName)
                  mail.ReplyTo = New MailAddress("sender@hello.com")
                  mail.Sender = mail.ReplyTo
  
                  If [to].Contains(";") Then
                      Dim _EmailsTO As String() = [to].Split(";".ToCharArray())
                      For i As Integer = 0 To _EmailsTO.Length - 1
                          mail.[To].Add(New MailAddress(_EmailsTO(i)))
                      Next
                  Else
                      If Not [to].Equals(String.Empty) Then
                          mail.[To].Add(New MailAddress([to]))
                      End If
                  End If
  
                  mail.Subject = "Testing Mail from Gmail Server"
                  mail.SubjectEncoding = System.Text.Encoding.UTF8
  
                  mail.Body = "HELLO WORLD"
                  mail.IsBodyHtml = True
                  mail.BodyEncoding = System.Text.Encoding.UTF8
  
                  'attachment
                  If attachment IsNot Nothing Then
                      mail.Attachments.Add(attachment)
                  End If
  
                  client.Send(mail)
                  success = True
              End Using
  
          Catch ex As Exception
  
          End Try
          ' end try 
  
          Return success
  
      End Function

  
  
  

• • Reply
  XuDong Peng

  Contributor

  2090 Points

  668 Posts

  Re: Failure sending mail (using Gmail Service)

  Feb 03, 2021 03:30 AM|XuDong Peng|LINK

  Hi kengkit,

  Google may block sign in attempts from some apps or devices that do not use modern security standards. Since these apps and devices are easier to break into, blocking them helps keep your account safer.

  For example, some third-party applications such as desktop mail clients ( such as Microsoft Outlook ,Mozilla Thunderbird,etc).

  Therefore, you have to enable Less Secure Sign-In (or Less secure app access) in your google account.

  After sign into google account, go to ---> https://www.google.com/settings/security/lesssecureapps

  You could also refer to this similar case:

  The SMTP server requires a secure connection or the client was not authenticated. The server response was: 5.5.1 Authentication Required?

  Best regards,

  Xudong Peng

  .NET forums are moving to a new home on Microsoft Q&A, we encourage you to go to Microsoft Q&A for .NET for posting new questions and get involved today.