We will test this and let you know. :)

Now we provide maintenance for some parts of a working server. So it may be the reason for that.

As a fast solution — you can write me Usernames of that accounts and I try to activate it manually.

Добавлено 3 дня спустя:

The problem seems to be solved. Please, test it. 

The new user registration email is not sending, as a colleuge of mine tried to register this morning, one with a private account and once again with a gmail account, neither of which sent the confirmation email. 

Even the most misconfigured mailhosts are accepted by gmail and end up in the spam filter.