Use of "Always send email notification" field

When the "Always send email notification" field is checked (on the user's management page)
the user doesn't get any emails from the group. I have noticed that the value of the mail_type
field in the og_uid table remains NULL while a record is added in the og_uid_global table for that user.
However it seems that the latter table is not used by the mail-out.pl script when it tries to find out the recipients
of a post.

In this case, on the user's "My subscriptions" page it is still possible to see the list of available subscription types although there is no submit button.