When I test in my account and your account, there's no issue adding a contact with a . in the middle of their name. I tested both the address mentioned and a junk test email, and they both went through fine. I also tested in my own account for the junk tester address, for both contact addition and account email verification, and both went through fine. I made sure to delete the contacts I added to your account, as well as the test list I made, to make sure those weren't polluting your setup if you wanted to avoid that situation.

You may want to check the addresses you're trying to add, to see if there's any other issues. Such problematic elements could include erroneous spaces on the end or beginning from copy-pasting, apostrophes, or some other element that may be causing import issues for the address.