unable to send email from SMTP in raspberry pi 4 - vb.net

Question

I have created a vb.net application to run in raspbian os. The application is supposed to send an email using SMTP. The code from the laptop can send the mail but in raspberry pi, it is not working it does not send any mail and it crashes the system.

Error message : default credentials are not supported

The code:

Imports System.Net.Mail 
Imports System.Data
Imports System.Net

Try
        Dim html As String = "<table cellpadding='5' cellspacing='0' style='font-size: 9pt'>"
        html &= "<tr>"
        For Each column As DataGridViewColumn In formPOS.ProductAddToCartDGV.Columns
            html &= "<th style='background-color: #B8DBFD;border: 1px solid #ccc'>" & column.HeaderText & "</th>"
        Next
        html &= "</tr>"
        For Each row As DataGridViewRow In formPOS.ProductAddToCartDGV.Rows
            html &= "<tr>"
            For Each cell As DataGridViewCell In row.Cells
                html &= "<td style='width:120px;border: 1px solid #ccc'>" & cell.Value & "</td>"
            Next
            html &= "</tr>"
        Next
        html &= "<tr>"
        html &= "<td style='border: 0px solid #fff'></td>"
        html &= "<td style='border: 0px solid #fff'></td>"
        html &= "<td style='border: 0px solid #fff'></td>"
        html &= "<td style='background-color: #dcdcdc;border: 0px;'><b> TOTAL ITEM: </b></td>"
        html &= "<td style='background-color: #dcdcdc;border: 0px; text-align: center;'><b>" & formPOS.useritemLBL.Text & "</b></td>"
        html &= "</tr>"
        html &= "<tr>"
        html &= "<td style='border: 0px solid #fff'></td>"
        html &= "<td style='border: 0px solid #fff'></td>"
        html &= "<td style='border: 0px solid #fff'></td>"
        html &= "<td style='background-color: #dcdcdc;border: 0px;'><b>SUB TOTAL: </b></td>"
        html &= "<td style='background-color: #dcdcdc;border: 0px; text-align: center;'><b>" & formPOS.userTotalLBL.Text & "</b></td>"
        html &= "</tr>"
        html &= "</table>"

        Using mm As New MailMessage("workserver@gmail.com", formPOS.customerEmailTb.Text)
            mm.Subject = "Smart Shopping Cart e-Receipt"
            mm.Body = html
            mm.IsBodyHtml = True
            Dim smtp As New SmtpClient()
            smtp.Host = "smtp.gmail.com"
            smtp.EnableSsl = True
            Dim NetworkCred As New NetworkCredential(mm.From.Address, "password")
            smtp.UseDefaultCredentials = True
            smtp.Credentials = NetworkCred
            smtp.Port = 587
            smtp.Send(mm)
        End Using
    Catch ex As Exception
        MsgBox(ex.Message)
    End Try

Answer 1

等待大神答复