In reply to a post by MHC:

Standard BT business provided

Right. Definitely appears to have more options than consumer Outlook.com accounts (to be expected I suppose).

If I was using a server that intercepted junk mail and put it into a folder without either letting me automatically download the folder or having a choice of non-interception I would be a little annoyed.

I have the filtering/interception turned off - deliberately as I found it would often catch legitimate messages and unless I checked daily I would never see them and as the criteria are always changing anything can get caught.

+1

I believe the general concept seems to be to force POP3 customers to periodically have to visit webmail (and eyeball some adverts) so that they can check for false positives in the spam folder. Google Mail is the same. Since your email (presumably) has no adverts, and (presumably) is funded by BT via your subscriptions, there's no need for them to do to do this on your account.

The spam folder can be made visible in the email client by utilising IMAP, though. Personally I prefer POP3, so I fully agree with your sentiments that email services should all have an "off" button for junk filtering.