When an email "bounces," it hasn't been delivered to its recipient for some reason. This could be due to a recipient's full mailbox or server error on either side. Though it may make sense to remove all addresses that bounce from your email marketing lists, there are certain situations where you would want to keep them.
Reasons Emails Bounce
Bounce rates are categorized into either hard bounces or soft bounces.
Soft bounces are normally errors on the user's side, usually a full mailbox. Major mail providers such as Hotmail and AOL store emails and process them at a later time when traffic isn't as high to avoid overloading.
These bounces result in delivery failure notification back to the sender after being processed, often with a "MESSAGE DELIVERY" error from a "postmaster" or "MAILER DAEMON" address. Most of the time, these bounces are temporary and resending the message later will solve the problem.
A hard bounce is frequently caused by a permanent error during the delivery process. It could be that your mail server is down or that the user's domain no longer works.
These are the bounces that you should consider taking off your address lists. Most email marketing clients automatically remove addresses that are categorized as hard bounces, some after only the first time.
Hard bounces could also be something that can be easily fixed, such as a misspelling. In that case, simply correcting the misspelling should fix the issue. Make sure this isn't the root of the issue before removing the contact from your list.
Ways to Prevent Bouncing
Too many repeated bounced emails can get your domain blacklisted for spamming. If you don't clean out nonworking email addresses, your analytics will be skewed, too, so it's important to keep your lists as clean as possible.
To minimize your bounce rates, make sure that all your client data is up to date. Double-check spellings of addresses in your lists. To ensure that your server is working, send a test message to yourself or coworkers before emailing your entire marketing list.
It's also a good idea to include an "unsubscribe" option in your email so users can opt to remove themselves from your list. Not giving them the option risks them marking your messages as spam, increasing your bounce rates.