Let me intervene here before giving you a solution. Since you're using ASP.NET, why are you using the .NET way of sending the emails. ASP.NET has their own method of sending emails, which makes sending emails in ASP.NET a bit easy and efficient for the developers.
You can read on sending the emails in ASP.NET from my article here:
Sending Emails Easily Using ASP.NET Helpers[
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Secondly, there are many servers that can be used to send the emails to clients. Gmail, Outlook or Yahoo all are the examples of free service providers, which can be used from hosting environment to testing environment and it works in both. I have personally always used the Gmail servers, although I do have Outlook and Yahoo accounts. You should also use these servers and they will work for you. An example code for setting up the environment to send email can be like this one,
WebMail.SmtpServer = "smtp.gmail.com";
WebMail.UserName = "<youremail@theirserver.com>";
WebMail.Password = "yourpassword";
WebMail.From = "SendersEmail@client.com";
WebMail.SmtpPort = 25;
WebMail.EnableSsl = true;
.. then sending the email code is as this one,
WebMail.Send(to: "recipient@example.com",
subject: "hi",
body: "message");
.. this would send the email, using above provided settings. This is pretty much easy, as compared to the MailMessage and the SmtpClient class provided in the .NET framework, as you're required to work with NetworkCredentials and other such setup too.