Setting a different "From" address for mail sent via Gmail using C#

Question

I am using a simple mail sender class that uses the System.Net.Mail. I need to update my application so various users can send email via it (using the same smtp account) but the "From" address should be of the user who is causing it to be sent. I tried setting the From property of MailMessage, and sending the from address into the constructor of MailMessage but nose of those worked. I am sure I am missing something simple or not understanding how the mail API works. Can anyone help?

Here my MailSender class that basically wraps the MailMessage, NetworkCredential and SmtpClient to provide one simple mail sending interface.

class MailSender
{
    private NetworkCredential credential;
    private String SenderAddress;
    private SmtpClient client;

    public MailSender(String ServerURL, String account, String password, String FromAddress = null, int port = -1, bool UseSSL = true)
    {
        if (port > 0)
        {
            client = new SmtpClient(ServerURL, port);
        }
        else
        {
            client = new SmtpClient(ServerURL);
        }
        credential = new NetworkCredential(account, password);
        client.UseDefaultCredentials = false;
        client.EnableSsl = UseSSL;
        client.Credentials = credential;

        if (FromAddress != null)
        {
            SenderAddress = FromAddress;
        }
        else
        {
            SenderAddress = account;
        }
    }

    public bool SendMessage(String to, String subject, String body)
    {
        try
        {
            MailMessage message = new MailMessage(SenderAddress, to, subject, body);
            message.From = new MailAddress(SenderAddress, "tester");

            message.IsBodyHtml = true;
            client.Send(message);
        }
        catch
        {
            return false;
        }
        return true;
    }
}

Answer 1

I just found out the answer by testing with another SMTP server. This is actually caused by GMail not allowing any other from address. This works fine with other SMTP servers.

Thanks to leppie, Mikael Svenson and smirkingman for their suggestions.