I have a Firefox Sync account since several years and use it on all my desktop computers, tablets, and mobiles. Now I try to connect my further installed mobile (Firefox Android) by this account, but I never receive a confirmation email (address is 100% correct, there is no spam, no junk, no trash!). I tried to create a new account with another email address in the same domain (my private domain): no success, no spam, no junk, no answer. And not blacklisted! I created a new account on another domain (my business domain): wow! this is working. But I'ld like to keep my private domain account! Re-installation of Firefox does not help.