S.N	Class	Description
1	Attachment	Represents an attachment to an e-mail.
2	AttachmentCollection	Stores attachments to be sent as part of an e-mail message.
3	MailAddress	Represents the address of an electronic mail sender or recipient.
4	MailAddressCollection	Stores e-mail addresses that are associated with an e-mail message.
5	MailMessage	Represents an e-mail message that can be sent using the SmtpClient class.
6	SmtpClient	Allows applications to send e-mail by using the Simple Mail Transfer Protocol (SMTP).
7	SmtpException	Represents the exception that is thrown when the SmtpClient is not able to complete a Send or SendAsync operation.

S.N	Property	Description
1	ClientCertificates	Specifies which certificates should be used to establish the Secure Sockets Layer (SSL) connection.
2	Credentials	Gets or sets the credentials used to authenticate the sender.
3	EnableSsl	Specifies whether the SmtpClient uses Secure Sockets Layer (SSL) to encrypt the connection.
4	Host	Gets or sets the name or IP address of the host used for SMTP transactions.
5	Port	Gets or sets the port used for SMTP transactions.
6	Timeout	Gets or sets a value that specifies the amount of time after which a synchronous Send call times out.
7	UseDefaultCredentials	Gets or sets a Boolean value that controls whether the DefaultCredentials are sent with requests.

S.N	Method & Description
1	Dispose Sends a QUIT message to the SMTP server, gracefully ends the TCP connection, and releases all resources used by the current instance of the SmtpClient class.
2	Dispose(Boolean) Sends a QUIT message to the SMTP server, gracefully ends the TCP connection, releases all resources used by the current instance of the SmtpClient class, and optionally disposes of the managed resources.
3	OnSendCompleted Raises the SendCompleted event.
4	Send(MailMessage) Sends the specified message to an SMTP server for delivery.
5	Send(String, String, String, String) Sends the specified e-mail message to an SMTP server for delivery. The message sender, recipients, subject, and message body are specified using String objects.
6	SendAsync(MailMessage, Object) Sends the specified e-mail message to an SMTP server for delivery. This method does not block the calling thread and allows the caller to pass an object to the method that is invoked when the operation completes.
7	SendAsync(String, String, String, String, Object) Sends an e-mail message to an SMTP server for delivery. The message sender, recipients, subject, and message body are specified using String objects. This method does not block the calling thread and allows the caller to pass an object to the method that is invoked when the operation completes.
8	SendAsyncCancel Cancels an asynchronous operation to send an e-mail message.
9	SendMailAsync(MailMessage) Sends the specified message to an SMTP server for delivery as an asynchronous operation.
10	SendMailAsync(String, String, String, String) Sends the specified message to an SMTP server for delivery as an asynchronous operation. . The message sender, recipients, subject, and message body are specified using String objects.
11	ToString Returns a string that represents the current object.

Imports System.Net.Mail
Public Class Form1
   Private Sub Form1_Load(sender As Object, e As EventArgs) Handles MyBase.Load
      ' Set the caption bar text of the form.   
      Me.Text = ""
   End Sub

   Private Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click
      Try
          Dim Smtp_Server As New SmtpClient
          Dim e_mail As New MailMessage()
          Smtp_Server.UseDefaultCredentials = False
          Smtp_Server.Credentials = New Net.NetworkCredential("username@gmail.com", "password")
          Smtp_Server.Port = 587
          Smtp_Server.EnableSsl = True
          Smtp_Server.Host = "smtp.gmail.com"

          e_mail = New MailMessage()
          e_mail.From = New MailAddress(txtFrom.Text)
          e_mail.To.Add(txtTo.Text)
          e_mail.Subject = "Email Sending"
          e_mail.IsBodyHtml = False
          e_mail.Body = txtMessage.Text
          Smtp_Server.Send(e_mail)
          MsgBox("Mail Sent")

      Catch error_t As Exception
          MsgBox(error_t.ToString)
      End Try

   End Sub