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Bounces, Black lists and Spam traps : What are the dangers for e-mail marketing and how can senders protect their reputation?

August 2018 by Certified Senders Alliance

Bounces are emails that do not reach the recipient for a number of reasons. Soft bounces are temporary problems such as a full inbox or an overloaded and unavailable server. In this case it can be possible to deliver the e-mails later. On the other hand, "hard bounces" are definitive problems such as non-existent addresses and we must not ignore them because this is the heart of the matter! In order to know whether it is a soft bounce or hard bounce, you have to look at the status code sent by the recipient’s server. If the code starts with 4, it is a soft bounce, if it starts with 5 it is a hard bounce, that is, a definitive error. If this error is a technical defect, it may be repaired and the corresponding mail address will become available again.

Those who believe they can ignore hard bounces fall into a dangerous trap because many Internet Service Providers (ISPs) and anti-spam filters take into account the "bounce rate", namely the rate of mails that are rejected as hard bounces. A particularly high percentage means that senders are not working efficiently, do not manage their address lists correctly or even send spam. In the worst case, senders are completely blocked by the provider. Therefore:
• Keep your lists clean and immediately remove bounces, at best automatically. At the very least, after the third bounce the corresponding address should be canceled from your mailing list.
• If you are not sure whether it is a hard bounce or a soft bounce, remove the address from your list.
• Make sure your bounce rate is never higher than 1%.
• Always use the Double Opt-In procedure to register new recipients.

Even if you always keep your mailing lists clean and immediately remove all hard bounces, you cannot avoid all the risks. There are also spam traps, that is, mail addresses which are used, among others, by ISPs and blacklist operators to identify potential spammers. Recycled spam traps are mail addresses of real people that have been disabled at a given time. Six to twelve months after disabling, such addresses can be reactivated as spam. Since no communication has taken place for a long time via this e-mail address, ISPs and blacklist operators assume that the senders of these e-mails do not adequately manage their mailing lists (for example, hard bounces are not canceled) and they put them on the blacklist. "Pristine spam traps" are mail addresses that are never used for communication, but only published as a decoy on the Internet and are a special form of spam trap. Intact addresses are usually detected by harvesters, programs that automatically search for email addresses on the WEB, which are then sold.

Once you are on a blacklist, it is very difficult to be removed from it. So what can you do to avoid ending up on the blacklist? Here are some tips to reduce this risk!

• Do not use sold or rented mailing lists
Never send e-mails to contacts on sold or rented addresses. This does not comply with the new data protection rules, it certainly affects your deliverability and you could eventually end up on a blacklist.

• Stop sending e-mails to addresses with hard bounces
Remove hard bounces from your distribution lists as quickly as possible. Invalid mail addresses can be activated after a certain time as spam traps and you will end up on a blacklist. Senders that have a bounce rate that is especially high will be considered as spammers and recipients will refuse to accept your e-mails.

• Pay attention to e-mails sent to addresses without receiving an answer
You should pay attention even to mail addresses that have not responded to your e-mails for a long time. In the worst case scenario this means that they are spam traps without real recipients. In the best case these are contacts that delete your messages without reading them or transfer them, annoyed, to the spam folder. Both cases harm a sender’s reputation. However, this mainly happens with consumer newsletters.

• Communicate regularly
Mail addresses you haven’t written to for more than six months may have become a spam trap without you noticing it, because you haven’t taken note of hard bounces. Special precautions must therefore be taken with address lists you have not been using for a long time.

The Certified Senders Alliance, a whitelisting project of the Electronic Commerce Association Eco E.V. in cooperation with the German Marketing Dialogue Association (DDV), allows a maximum bounce rate of 1% in its criteria. To avoid bounce handling from becoming a problem, CSA experts advise you to always use the double opt-in procedure to register new recipients. Here you will find the criteria for CSA admission: Https://

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