A connection attempt failed because the connected party did not properly respond after a period of time, or established connection failed because connected host has failed to respond 173.194.79.109:25

I am using asp.net 4.0 and Access 2010 as the database.I need to send the mail whenever a leave request is submitted and it was working fine when i run it in the local host.when i put the application in the web hosting server and try to submit the leave request,following error is shown during sending the mail: "A connection attempt failed because the connected party did not properly respond after a period of time, or established connection failed because connected host has failed to respond 173.194.79.109:25"Can someone help me to resolve this issue for me?We are using windows server 2003 as the web hosting server.Below is my code for sending the mail:
Public Shared Sub sendmail(ByVal strto As String, ByVal strfrom As String, ByVal strsub As String, ByVal strbody As String) Dim objfrom As New MailAddress(strfrom) Dim objto As New MailAddress(strto) Dim objmail As New MailMessage(objfrom, objto) objmail.Body = strb ...