As one of my all-time favorite authors famously said, "There's no such thing as a free lunch." (Robert Heinlein). If you want a free mailbox, expect to get exactly what you paid for. I prefer unseen.is.
Merry Christmas from a chilly Vancouver Island!
...if you aren't paying for the product, you ARE the product.
But even for free, I expect spam and marketing, but not having accounts and personal data stolen (several times). There are many free services which are better protected, private, and more safe. If I were Verizon, I would want a serious discount on the purchase valuation price. Just to clean up the mess will be costly.
Stay warm on Vancouver Island.