Many companies upload their email marketing list once, and forget about it forever more. But if you repeatedly ignore bounced emails, it could cost you in the long run.
Bounces fall into two categories:
1) Hard bounces. These are permanently bad addresses, either due to a typo (such as no @ sign) or because the person has changed their email address. Always a significant factor, out-of-date email addresses have risen in the last year due to people who have lost their job and, along with it, their business email address.
2) Soft bounces. These are due to temporary problems, such as full mailboxes or servers that are down.
Repeatedly mailing to email addresses that bounce flags looks to ISPs like the behavior of a spammer. The reputation of perfectly legitimate companies can suffer as a result, resulting in lower deliverability or even blacklisting.
If you use an email service provider to deploy your email, they’ll place email addresses that repeatedly bounce on a “do not mail” list in order to protect their own reputation. However, if you pay your email service provider based on the number of names you have uploaded, you’re likely to be charged for those bounced names until you remove them from the system.
Either way, it’s a good idea to periodically review email addresses that bounce repeatedly, correct those you can, and remove the rest.