Here is the scenario:
There is a group of people (e.g. 3), who are receiving the same e-
mails, although only one of them has to respond to every received e-
mail. The amount of e-mails received daily is hundreds.

Is there a way to mark the e-mails that were already responded to
(e.g. by adding a specified colour or some other marker)? This way all
of those people (in this example 3) won't have to go through all of
the e-mails, but just through the ones that didn't get a response so
far.

Thank you for your responses,
Stiepan