Nowadays a rapidly rising proportion of e-mails from legitimate providers with the necessary permissions are being unjustifiably classified as spam and are disappearing into cyberspace without a trace. This is the result of two factors: exponential growth in the spam software segment and to some extent irresponsible use of spam software by network administrators.

Thus, you can never really determine whether or not your e-mails reach their destination unless you monitor the various areas that affect deliverability as well as your statistical delivery rate.