No PM, no e-mail. Just show "unhandled notifies" in some way above the forum.
At our board I made a hack to do this. Notifies are put in a table, with a "handled or not" flag, and if you are a moderator/admin you get to see in the header the number of unhandled number of notifies.
All 14 of us are global admins/mods, so this saves a lot of e-mail load. We really had a problem when coming home after a day that your e-mail box would be full of notifies and every mod/admin had to wade through all of them to see if they were handled or not.
With this system, our response times to notifies have become significantly faster, none are forgotten anymore in the bulk, and mods/admins are not bothered anymore with notifies that are handled already. As an added bonus, we also have statistics of who use the notify option the most and maybe use that information to see if somebody would fit in your moderatorteam.
b.t.w., on the example image, it's called a "Fluitje", that's whistle in english, and that's how we call them at our board.
My header also notifies in case of new user registrations, new unapproved posts, new displayname change requests. And new user registrations/display name changes are only shown to the admins that keep themselve busy with that.
This was my reaction to a post on ubb central on using PM's for moderator notifies.
I spend a little this time week translating everything (I was smart enough to do all tables and stuff in dutch) and changed the code that's within ubb.threads to do it ubb.threads style.
The actual code outside ubb.threads that displays the notifications is messy, has one major bug, and needs to be rewritten.
The current system is also just based on global mods/admins. Everybody sees every notify. It does not check if you are admin or moderator of that specific board.
I am planning on a rewrite of this myselve in the near future.
Able to handle a notify for yourselve, but leave it open for others (for instance, if you can't handle it, but you know somebody else can)
More stuff to be viewed on a post in the notifies script
The version I uploaded here is actually something like version 0.01 alpha that worked so well while using it I never got around to adding the stuff I wanted.
You want to take a look? Then take a look at the attached zip file.