They appeared. Later since it followed the data dumps.
No mails since "NGS Bug fixes 2011-09-21"
I have been receiving them normally, so it might be something in your subscribed entities that is triggering a problem (some specific character set maybe? No idea...)
I'm seeing this too. My last email from MusicBrainz was on the 21st and I normally get a subscriptions email every single day.
I'm raising the priority of this to "Major" (can be lowered again if this was not correct), because this bug means that people who comment on my edits (or edits where I asked a question) will probably never get an answer... it really affects editing . I created MBS-3531 before seeing this, I don't know if the two are related.
This was since fixed again