Zanata allows invalid email address, fails to send verification email
On registrations, there are certain email addresses can be entered and stored, but are not valid and will be rejected by sendmail (or equiv.). This results in the account being locked out to the user, an error displayed, and no indication the account was actually created.
For example, the address "email@example.com+" was accepted, but the '+' is not valid in that position.
The workaround is for the user to enter the email and password and use the "Inactive account" feature to update their email to a correct one.