TestableEmailer is a product that grew out of
this need. It is a thin wrapper around MailHost that allows
for a "test mode". When this mode is turned on,
rather than sending the mail through the Mail Host the product
stores all the information in the email. This can be retrieved
later and assertions made against what is expected from that
TestableEmailer has been built using Five interfaces
and views. It has been tested on Zope 2.8.6.