The federated nature of e-mail is degrading. Most recent example: My kid just registered with CCCApply (the central website for California Community and City colleges).

It took a while. Finally after calling support I found out that the e-mail you get your confirmation code to doesn't work with most e-mail providers (they said custom e-mail domains hardly ever work, Yahoo e-mails never work, Outlook is iffy) so please register with a gmail address (and they offered to help me sign up for gmail if I didn't have it).

An older example: According to a Macy's CS rep, Macy's won't deliver their e-mails to domains registered with godaddy (the actual e-mail provider apparently doesn't matter, but in this case it was Microsoft). My mom has an account with them that she can't access, because she needs to receive an e-mail to login, and she needs to login to change which e-mail address is associated with it.