Inbox.com's phone number (as listed on this site) is not a working number. Neither is the phone number of Xacti Group, Inbox's parent. For me, the site went down yesterday before noon, and has remained inaccessible--and along with that, all information my account (yes, paid for) contains or contained.
Having read the following two articles, the second from April of this year, I've little hope that the inbox.com site will reappear.
https://www.nytimes.com/2016/11/30/magazine/how-to-hide-400-million.html
https://www.dailymail.co.uk/femail/article-*******/Mother-reveals-ex-husband-s-FORTUNE-sparked-divorce.html
From the look of things, Inbox and Xacti were part of an unraveling web, and may have been dissolved as part lengthy court cases.