Sent an email using Shared hosting mail address provided by

I have purchased a domain + hosting from Nexus , Now they have given me ten pop up accounts i have to send an email to different domain address like gmail,hotmail,yahoo and some other company specific domains, M i able to send an email by giving my hosting mail server domain Ip and port number into my code and providing the email credentials , I have tried that but some times it send email some times it give an error that cannot connect to the server , when I contact the hosting provider they said that You cannot send an email by that provided mail server , because you have a shared hosting . I think this should nt be like that , below is my code to send an email

Private Sub SendHtmlFormattedEmail(ByVal recepientEmail As String, ByVal subject As String, ByVal body As String)

Dim mailMessage As System.Net.Mail.MailMessage = New System.Net.Mail.MailMessage

mailMessage.From = New MailAddress(ConfigurationManager.AppSettings("UserName"))

mailMessage.Subject = subject

mailMessage.Body = body

mailMessage.IsBodyHtml = True

mailMessage.To.Add(New MailAddress(recepientEmail))

mailMessage.From = New MailAddress("[email protected]")

Dim smtp As SmtpClient = New SmtpClient

smtp.Host = "IP"

smtp.EnableSsl = False

smtp.Credentials = New System.Net.NetworkCredential("[email protected]", "Password")

smtp.Port = PortNumber

smtp.Send(mailMessage)

End Sub