Hmmm.....
The reason they restrict you is to prevent spam I would guess (which is a good thing IMO)
The thing is (no offence here
), you are using a residential home BB connection for business use, so I'm not sure you really have a leg to stand on.
I would have a bit more respect for Wanadoo if they actually told you that, rather than off fob you a couple of lame BS excuses to prevent them helping you.
What about creating a new mailbox, & using that just for your business stuff, & change the 'reply to' address to your work address?
Not ideal I know, but probably better than nothing?