What is an 'Email Bounce' and what can I do about them?

In general, an “email bounce” means that the email that you have sent to a specific address is not delivered – the mail server sends it back. The bounce rate is one of the most important metrics that you have to monitor after you’ve launched a bulk email campaign.

Why does this happen and how can it affect you as an email sender?

Here’s where “hard” and “soft” bounces comes in.

A soft bounce is an email that has not been delivered to your recipient because of temporary reasons. It might occur because the email is too large, the inbox is full or the email server is down. In this case, email service providers send the email repeatedly, e.g. Soundest trying to reach the recipient 8 times in 12 hours. Soft bounces are not as dangerous as hard bounces.

A hard bounce is an email that is sent back due to permanent reasons. The reasons for this can be various. Most of the time, the recipient’s’ email address is invalid or no longer in use:

• the domain (email ending after @) does not exist;
• the server is not accepting emails;
• the address is mistyped (name@example.cam instead of name@example.com, etc.)

The thing is, bounces damage your deliverability rates and sender reputation – you can be treated as a fake email sender. This status will spoil your email deliverability tremendously.

Typical reasons for high hard bounce rates. What should you do?

1. As a sender you use free email service like Gmail, Yahoo or AOL. In order to reduce deceitful emails, many email service providers have changed their DMARC policies. According to this policy, your emails will not pass the authentication and will be bounced. So you should use the email with your private business domain (name@yourbusinessdomain.com).
   
   
2. Your list is out-of-date. If your list of subscribers was built several years ago and you decide to use it only now, don’t be surprised of a high bounce rate. Your subscribers have probably changed their emails, forgotten about you or are no longer interested in your content. In this case, you should delete users who have been inactive for months. Also, send a re-confirmation email to your entire subscriber list.
   
   
3. If your subscriber list is brand new but the bounce rate is high, the problem might lie in the way it was built. People tend to mistype their emails. So you can skim the list and check for simple mistypes like @gnail.com, @yahoo.kom, etc.

Another way to control this is an email verification or double opt-in method after the signing up. In this way you will be certain that the address you are marketing is functional. Double opt-in lists have much higher engagement level. Using this method, people are not able to sign up with fake email addresses – they have to be valid to opt-in.

Take home message

High hard bounce rates have a big negative impact on both the sender’s reputation and email deliverability rate.  Using the email marketing channel, you should strive to keep your bounce rate low. The lower it is, the better.

(Source: https://www.omnisend.com/blog/bounces-email-deliverability-troublemakers/)