I'd suggest (as a falsehood): Users always have immediate access to their mailboxes I imagine lots of people do not have their email account attached to their

I'd suggest (as a falsehood): Users always have immediate access to their mailboxes I imagine lots of people do not have their email account attached to their phone, people maybe on a shared computer (library perhaps) and do not readily have access to the password (if it's randomly generated and stored at home) or their mail provider is blocked where they are (things like Hotmail etc. were blocked whilst I was in education) I'd say there's lots of services that require you to validate your email address immediately after signing up - even where an email address is not required by the service itself - having a grace period to verify you email in such circumstances is great, but see it very infrequently.