People can get very worried about how to send documents to other people during the tribunal process. They fear somehow doing it wrong.
This is almost always totally unnecessary. All the normal sorts of methods are fine — post, fax, email, hand-delivery. As is any abnormal method as long as it works. If you can persuade a carrier pigeon to drop off your application for disclosure at Watford ET, go right ahead.
Use common sense. Don’t fax someone a 1,000 page bundle — it will jam up their fax machine and annoy them. If something is urgent, don’t use a 2nd-class stamp. If your opponent persistently claims not to receive your communications, consider using registered mail.
But otherwise, use any sensible method you like.