Send Mail Async In Asp.net -

i have code

protected void aspxbutton1_click(object sender, eventargs e) {     mailmessage mail = new mailmessage();      mail.from = new mailaddress("paragonadmin@qss.co.za", "paragon admin");     mail.to.add(new mailaddress("dewald@qss.co.za", "appointment scheduled"));     mail.subject = "enter mail subject";     mail.body = "enter mail body";      smtpclient smtpclient = new smtpclient("smtp.qss.co.za");     smtpclient.credentials = new system.net.networkcredential("paragonadmin@qss.co.za", "123456");     object state = mail;      //event handler asynchronous call     smtpclient.sendcompleted += new sendcompletedeventhandler(smtpclient_sendcompleted);     try     {         //smtpclient.send(mail);         smtpclient.sendasync(mail, state);     }     catch (exception ex) { /* exception handling code here */ } }  void smtpclient_sendcompleted(object sender, system.componentmodel.asynccompletedeventargs e) {     mailmessage mail = e.userstate mailmessage;      if (!e.cancelled && e.error != null)     {         aspxlabel1.text = "mail sent successfully";     } } 

it supposed send mail asynchronous in application, reason "failure sending mail" error message.

any advice