From time to time we get questions concerning email address verification. Though many SMTP servers allow the verification of email addresses there are probably just as many that don't allow it. So, email verification at it's best is about 50% accuracy using the method the internet RFC guru's designed. Thanks to SPAMers this built in verification system is not very usable, especially with the big email providers.
Campaign Enterprise and Email Marketing Director do not have this email verification capability mainly because doing mass email verification can cause your SMTP server to become blacklisted. Many SPAMers use this technique with fabricated email lists in hope of getting valid email addresses (ie: email@example.com, firstname.lastname@example.org,...). So while it is an important thing to keep your list clean it should be done as if you were a normal one-at-a-time emailer that gets a bounce when the email is bad, then you don't send to it again. When you send out the first email campaign on a new list you will receive bounces if the email addresses are not valid. It is important to receive these emails and mark them as bounces to not send to them again. There are two reasons for this: First, you don't want your campaign to waste time sending to these addresses again. If your list is small, this may not matter, but if your list is big, or you are paying for each email sent out through a service, it is especially important. Second, if you keep sending emails that bounce your SMTP server will acquire a bad reputation will eventually get blacklisted.
There are verifications services that specialize in the field of email list cleaning that have good internet reputations, are known for being good citizens of the internet, and are allowed mass verifications of lists. One of them we recommend is http://freshaddress.com. You send them a list and they will make sure each address is usable, and they also do other services like email forwarding if the email address has changed.
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Taking the time or spending the money to get your list clean will have many benefits over the cost. If you try to save money here and do it marginally you may end up spending a great deal more in time and money trying to get your SMTP server off blacklists.