Reputation improvements from Expired emails

[Joshua Baer]

I was chatting with Aaron at Living Social about this idea today and
he brought up a potential benefit that could be use to incentivize
senders to adopt this. More and more, user engagement is factoring
into spam filtering and the "priority" of a message. If users don't
open or click on your emails then you're more likely to go to the spam
folder.

It would seem to make sense that if the sender marks a message with an
expiration date, then they shouldn't be penalized for that message
being "inactive" after the expiration date. If there was some way to
work that into the reputation algorithms it would a "carrot" that we
could hold out in front of senders to encourage them to adopt the
header and to select the right date for the expiration date.

Thoughts?

~Josh