Adding multiple lines to body of SMTP email VB.NET

Just treat it like a normal text object where you can use Environment.NewLine or vbNewLine between sentences.

StringBuilder is useful here:

Dim sb As New StringBuilder
sb.AppendLine("Line One")
sb.AppendLine("Line Two")

mail.Body = sb.ToString()

I would create a variable for your body and then add that to the mail.Body so it would look something like this.

Try
    Dim strBody as string = ""
    Dim SmtpServer As New SmtpClient
    Dim mail As New MailMessage
    SmtpServer.Credentials = New Net.NetworkCredential()
    SmtpServer.Port = 25
    SmtpServer.Host = "email.host.com"
    mail = New MailMessage
    mail.From = New MailAddress("[email protected]")
    mail.To.Add("[email protected]")
    mail.Subject = "Equipment Request"
    strBody = "This is for testing SMTP mail from me" & vbCrLf
    strBody += "line 2" & vbCrLf
    mail.Body = strBody

    SmtpServer.Send(mail)

catch ex As Exception
    MsgBox(ex.ToString)
End Try

That will append the line breaks and you should have each line on it's own in the email.

If the body of your message needs to be in HTML format, add the <br> tags right in your String. vbCrLf and StringBuilder don't work if the body is in HTML format.

Dim mail As New MailMessage
mail.IsBodyHtml = True
mail.Body = "First Line<br>"
mail.Body += "Second Line<br>"
mail.Body += "Third Line"

If it is not in HTML format, the other answers here appear to be good.