I need to test that a series of sites are up and running and that they can send and receive email.
Step one: send email from email@example.com
Step two: expect response email emailServerOne@example.com within a given amount of time.
If those are the only requirements then a simple (well, not so simple but not very complex) script in Perl, Python or your favorite scripting language will achieve the same results for free with greater flexibility.
You should take a look at Febooti. It is an open-source program that can create/send emails. I was using it prior to send an email with test results every morning once my test suites were finished.
Parasoft SOAtest would be able to handle this. It would enable you to send emails and apply a time based assertion on receiving the response. On a failure it could then email you with an alert. http://www.parasoft.com/jsp/products/soatest.jsp