【C#】Smtp发送邮件

class SmtpEmail
{
SmtpClient smtpclient;
MailMessage msg;
Attachment attachment;
public void sendMail(String form, String[] to, String subject, String body, String attachmentpath)
{
if (to == null || to.Length <= 0) {
return;
}
try
{
smtpclient = new SmtpClient("smtp.URL");
smtpclient.UseDefaultCredentials = true;
smtpclient.Credentials = new NetworkCredential("username", "*****");
smtpclient.DeliveryMethod = SmtpDeliveryMethod.Network;
msg = new MailMessage();

for (int i = 0; i < to.Length; i++)
{
msg.To.Add(to[i]);
}
if (msg.To.Count <= 0) {
return;
}
msg.From = form;
msg.Subject = subject;
msg.Body = body;
if (attachment!=null && !attachmentpath.Length.Equals(0))
{
this.attachment = new Attachment(attachmentpath);
msg.Attachments.Add(attachment);
}
msg.BodyEncoding = Encoding.UTF8;
msg.IsBodyHtml = true;
smtpclient.Send(msg);
}
catch (Exception err)
{
MessageBox.Show(err.Message);
return;
}
}
}