This is the link that arived to mail indox:
moodle sends the self registration email in html, encoded as quoted-printable.
The equal sign is lost whith quoted-printable encoding.
I have a 2 possible solutions:
.1 lib/moodlelib.php line 5872: $mail->Encoding = '8bit'; // before quoted-printable
.2 lib/moodlelib.php line 6097: $data->link = $CFG->wwwroot .'/login/confirm.php?data=3D'. $user->secret .'/'. $username; // added 3D