Timeout error when sending email using System.Net.Mail

I am trying to send an email from a web form. The email service in our company is offered by the ISP (using our domain name) so I talked to them to get the correct information about how to contact the host (email server). The code I use to send the email is shown below but I get a timeout exception. Employees in our company use MS Outlook to send/receive email so I double checked the parameters and they are the same the ISP gave me.

SmtpClient objSmtpClient = new SmtpClient();
objSmtpClient.Host = "the ISP email server here";
objSmtpClient.Port = 465;
objSmtpClient.EnableSsl = true;
objSmtpClient.Credentials = new System.Net.NetworkCredential("an email account here", "password here");
objSmtpClient.Send(objMailMessage);

I have already tried several workarounds I have found searching the Internet without success.
I will very much appreciate your feedback.

Respectfully,
Jorge Maldonado