I have a client who sells advertising at her website and in her e-zines, and because of this, she is hesitant to remove hard bounced email addresses from her mailing list. She mistakenly believes that she can charge more for her newsletter advertising by saying her email list is so many names big - even though at least 20% of those email names are "no good". I've been trying to convince her that she is doing more harm than good, and I thought I'd share some facts with you to prevent you from making the same mistakes.

First, it's important to differentiate between hard-bounces and soft-bounces.

A soft bounce refers to a message that was delivered to the mail server, but the message could not be delivered to the actual mail box. The server might have timed out because it was currently dealing with too many messages, or the recipient's mailbox might have been full, or the email message might have been too large.

A hard bounce refers to a permanently undeliverable message. You might be sending a message to an invalid email address (check your addresses for typos), the mailbox might have been closed or the mail server might refuse messages coming from your email address.

Generally, I recommend resending a hard bounced message only one time, approximately four days after the first message. If the second message still does not go through, and if you can not figure out how to fix the issue, it's important to completely remove the address from your list.

If you do not remove the undeliverable email addresses from your list, your own email address could get blacklisted. And the worst part is, you may never even know it. When an ISP is hit over and over again with bounced messages, it can trigger a red flag. The ISP sees the messages are coming from you, and they simply block all future incoming messages sent from your email address or your IP address. If that happens, you won't even be able to send email to the "good" addresses on your list.

And, since many ISPs are now sharing this blacklist information, your mail can literally be blocked from hundreds of recipients. (You may have heard the term "sender reputation" bandied about.)

While it may seem counterproductive to remove email addresses from your mailing list, the process will actually leave you with a more effective list and a more efficient marketing campaign.