This works with hotmail and gmail but doesn't seem to work with yahoo (others please let me know).
When you see a "new customer's only" in the terms and conditions so have to create a whole new email account and it takes forever.. Don't.
You can add a + to your standard email address and the emails will still come to your usual email address without need to create a new account for email.
The + (plus what you add) must come just before the @
So suppose your current email address is email@example.com
you can change it to firstname.lastname@example.org
and you will still get the emails.
This will save creating a new mail address when creating a new customer account for a sign up offer.
You can use + and anything else, so for a new asos account you could use +asos1 and then +asos2 and so on..
This does not fool all vendors but does work for many and might save some time for you guys.