In beta cluster confirmation is never received when
- a new user is created and enters email address on Special:CreateAccount form
- a user changes an email address
A new email address is successfully added in db - e.g ET198.
The email address (not wikimedia based) that was used in the above cases is the same address to which emails are presently successfully delivered (for users who have been confirmed their address previously, e.g. ET4).
Emails are sent without any problems for all kinds of notifications for confirmed email addresses.