The code works fine in Windows. It's :
************************************************************
Dim LectorConfiguracion As New AppSettingsReader
Dim oSmtpClient As New System.Net.Mail.SmtpClient
Dim oMailMessage As New System.Net.Mail.MailMessage
Dim EmailHost As String = ""
Dim EmailFrom As String = ""
Dim EmailTo As String = ""
Dim EmailUser As String = ""
Dim EmailPasswd As String = ""
EmailHost = LectorConfiguracion.GetValue("EmailHost", EmailHost.GetType())
EmailFrom = LectorConfiguracion.GetValue("EmailFrom", EmailFrom.GetType())
EmailTo = LectorConfiguracion.GetValue("EmailTo", EmailTo.GetType())
EmailUser = LectorConfiguracion.GetValue("EmailUser", EmailUser.GetType())
EmailPasswd = LectorConfiguracion.GetValue("EmailPasswd", EmailPasswd.GetType())
oSmtpClient.Host = EmailHost
oSmtpClient.Port = 25
oSmtpClient.Credentials = New System.Net.NetworkCredential(EmailUser, EmailPasswd)
oMailMessage.From = New System.Net.Mail.MailAddress(EmailFrom)
oMailMessage.Subject = Subject
oMailMessage.To.Add(EmailTo)
oMailMessage.IsBodyHtml = False
oMailMessage.Priority = Net.Mail.MailPriority.Normal
oMailMessage.Body = Body
oSmtpClient.Send(oMailMessage)
************************************************************
The error happen in then line : oSmtpClient.Send(oMailMessage)