According to RFC 2076 Section 3.8 there is no standard way to send the expiration date.
Expiry-date -headers exist but, as said, they are not standardized. Quick look through some newsletters in my inbox confirmed that these are not commonplace.
Some e-mail clients can send this header with the email. I just tested it with Outlook 2007 and the expiration-related part in the message header looks like this:
Expiry-Date: Fri, 10 Dec 2010 18:00:00 +0200
(It is funny to notice that the used header is
Expiry-Date which was tentatively designed (in 1997 ie. 13 years ago) to be replaced with
Expires header. But this just shows how obsolete its usage is)
It might be in use in some corporate environments where it is known that every e-mail client can use the expiration header, in Outlook to Outlook type of messaging for example.