[Design] request: "if corresponded with recently" filter condition

[Kaitlin Duck Sherwood]

I'd like to see a filter condition that works out to be "if I haven't 
corresponded with the sender in <time range>".

The biggest reason for this is vacation messages.  I want pretty fine 
control over my vacation messages: I want them to go to my friends 
and business colleagues, but I don't want spammers, stalkers, or 
mailing list members to get my vacation messages.

One way to implement this easily is to have an address book full of 
recent senders, coupled with the "is in address book" filter 
condition:
	when a message arrives
	if
            sender is in the PeopleIKnow address book
	and
	   sender is not in the RecentCorrespondents address book
	then
            reply with OnVactionInBhutan template

(Note that for this to work well, I want to be able to empty the 
RecentCorrespondents address book right before I go on vacation.)

-- 
Kaitlin Duck Sherwood
Author of the _Overcome Email Overload_ series, http://www.EmailOverload.com