error 8004020F

[gariboldo]

Have all a nice day,
I have the following problem:
I have in my site a page ASP that contains a form and i'm trying to
send it to an email address with the following script:

Set cdoConfig = CreateObject("CDO.Configuration")

With cdoConfig.Fields
.Item(cdoSendUsingMethod) = cdoSendUsingPort
.Item(cdoSMTPServer) = "mail.server"
.Update
End With

Set cdoMessage = CreateObject("CDO.Message")

With cdoMessage
Set .Configuration = cdoConfig
.From = "(e-mail address removed)"
.To = "(e-mail address removed)"
.Subject = "xxx"
.TextBody = "yyy"
.Send
End With

Set cdoMessage = Nothing
Set cdoConfig = Nothing

That work when in the .Item(cdoSMTPServer) i put the mail server of
the provider which i am connected to (which is not the same of my
site), but when i put the mailserver of my site i get the error
8004020F. It seem as my provider don't let pass my messages if i don't
use his mailserver. I need the form could be send from everywhere,
what can i do?
Thanks in advance for the answers