set outlook message expiry via workflow

Hey there All,

We have SharePoint and Nintex 2010 installed and in use for some workflows.

A user has enquired about 'expiring' the email notifications that the workflows create to aid their personal inbox management.

I have looked in the 'Send a notification' settings and can see nothing obvious.

Is there a way to set this in a workflow anywhere?

Thanks in advance,

Trent