Fax straight to faxnr in OL2003/Exchange gives error

[fmientjes]

In OL 2003 (with Exchange) I want to send a fax to a faxnumber.
In the To box I type: [faxto:+313456789]
After a few seconds OL changes it to +31345678 (underlined), so it looks like it is recognized.
After sending I immediately get an error e-mail, saying that "via no e-mailaccount it is possible to send to this recipient"

However, if I create a contact with the right faxnumber and I'll send the same e-mail to the contactperson (instead of straight to the faxnumber) it works fine!

Is there a way of sending a fax without creating a contactperson first?

Thanks,
Frans