There are a number of times that we need to test just the content of
the email we send from code. (eg. text and formatting is correct)
without actually needing to send the email.
You can dot this by setting the smtp client's DeliveryMethod property to
SmtpDeliveryMethod.PickupDirectoryFromIis.
Of course this assumes that you use System.Net.Mail.StmpClient. Also,
you'd need IIS installed BUT it's NOT necessarily running/starting.
Without
knowing this, I previously had to use setup my IIS SMTP virtual server
or use a valid stmp host (will fail if the host is invalid) and wait
for the message to arrive at my inbox (which at times takes forever
without me whether there is something wrong with my code or the host).
Furthermore, you free yourself from risk of spamming other people (especially clients) or even yourself.
And of course for mail concerns, the link has always been a great (if not the greatest) resource
http://www.systemnetmail.com/default.aspx