I know the answer has been accepted, but I'm going to give a differing viewpoint - at least for internal company emails. Thank you responses should be the exception, not the norm. Most professionals receive so many emails every day that entire chapters of books have been dedicated to managing email. If everyone that I respond to sent a thank you, the number of emails with no business value that I have to sort through would increase by about 50%.
There are exceptions of course. Examples are: when someone goes way above and beyond and should possibly be praised amongst coworkers; when you are dealing with people from other departments that you don't know and rarely interact with; external contacts that you rarely deal with.
In short, for people that you work with frequently, I don't believe it is required and will actually add noise to their inbox. What starts out as a formality could quickly turn into an annoyance. For infrequent contacts, I would encourage it.
Caveat- I would add that there are situations where some people, no matter how frequently you work with them, should always get a thank you. Some people do not get that much email and are a bit more traditional, expecting a thank you for every response. You will have to use judgement.