How to send Email from any Email ID in from field in C#

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C#

Hello everyone,

I m developing a website for Email Marketing.
User can register on my site by his/her any
existing(gmail,yahoo,etc.) email id.

While sending mail.I want my User's id to be
displayed in from field.

i.e.

mail.From = new MailAddress("UsersRegisteredEmailID");

while mail should be send my email id and my domain.
It is possibe ???

My Code:

MailMessage mail = new MailMessage();
        mail.From = new MailAddress(Users_Email_Address);
        mail.Subject = Subject;
        string content = Content;
       
        SmtpClient client = new SmtpClient();
        client.Credentials = new System.Net.NetworkCredential(MyEmail-Id,MyPass);
        client.Port = 587;
        string p = HttpContext.Current.Request.UserHostAddress;
        client.Host = "smtp.Mydomain.com";
        client.DeliveryMethod = SmtpDeliveryMethod.Network;
        AlternateView av1 = AlternateView.CreateAlternateViewFromString(content, null,MediaTypeNames.Text.Html );
       
         mail.AlternateViews.Add(av1);
        mail.IsBodyHtml = true;
        mail.To.Add(To_Address);
        client.Send(mail);

Pls Help...

Thanks