Changing the extention can be an added security feature. Scripts that hackers created would most probably bypass that URL as it could be treated as an invalid URL since the extention is customised.
It can also, on the other hand, be a dangerous script running on a private server that could be programmed to steal information. Scams, and look-a-like webpages can be done with such extentions, and obtain user's information without the user knowing. Because the extention can be customised, it's sometimes not easy to spot the differences between a real URL and the scam URL in a glance. Users may just click the link in their email without much thinking, assuming the email is a real document.
Reply