Nobody likes to waste money. Your customer database must remain clean, constantly appended, and updated with the most recent information. It's not just about saving money, though. An inaccurate database can make your overall email marketing completely ineffective.
A dealer once told me that they didn't worry so much about cleaning their database because it only cost them pennies for each wasted email they sent. It would take time to go through and eliminate even 100 email addresses and it would only save him a couple of bucks. This is the wrong way to look at it because there's an important aspect of email marketing that wasn't being considered.
The ability to deliver emails through modern spam filters is an absolute key to success. A few percentage points different on a large list can be thousands of emails lost in cyberspace. Getting emails to make it into inboxes is a function of several different factors, including the trust value of the email server, the wording within the email, the presence of items such as images and links, and the trust value of the domain itself. When emails are sent out, servers receiving these emails will scan them, determine if they're spam or not, and try to place them in the inboxes.
When an inbox no longer exists, this is a negative. Enough of these delivery failures can have a detrimental effect on your ability to get your emails through. Even simple aspects of purging email addresses such as unsubscribes can cause your emails to stop making it through if you're not following through with the requests. This is why having a strong and savvy email marketing company on your side is imperative to the success of your database marketing.
Database marketing isn't just about messaging. Reach is an incredibly important aspect. If you're not doing what it takes to reach people and avoiding the things that can prevent it from happening, you're not just hurting yourself with the bad records. The good records can be affected as well.