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Bounce rate and Spam complaints
Bounce rate and Spam complaints
Räftegård, Elin avatar
Written by Räftegård, Elin
Updated over a week ago

Bounce rate and Spam complaint

In this Article

Bounce rate

You may already be familiar with the concept of deliverability rate. Bounce rates reflect the opposite: while deliverability rates compares the number of the emails that reached an inbox with the number of emails sent, bounce rates compare the number of sent emails and the ones that did not reach a recipient. By definition, then, an email's bounce rate reflects the number of emails rejected by the receiving server.

All Email Reports contain information about the delivery details of your email sending. To see which Profiles bounced and their corresponding bounce code and reason, export the Bounces section of the Email Report.

Email bounces can be divided into three categories: soft, hard and technical.


A soft bounce is caused by a temporary error. For example, full inbox or receiver's server is currently too busy. The sending will be retried every hour for up to 48 hours after the initial send time. No further action will be taken.

Soft bounce reasons (codes)

3001: Soft - Mailbox is full

3002: Soft - Recipient email server is currently too busy

3003: Soft - Email account is inactive

4000: Soft - General error

4004: Other - Unknown


Hard bounces are the ones to look out for!

A hard bounce occurs when it was impossible to deliver the Email. Reasons could be email address do not exist, email domain does not exist or closed email account.

Once a hard bounce happens, we won't make more attempts to deliver to that profile in the Email tool activity where the bounce happened.

If a hard bounce happens three (3) times for the same profile, APSIS One will stop sending emails to the Profile altogether. However, consent for the Profile will not be removed. Note that SMS bounces are treated the same in APSIS One.

Hard bounce reasons (codes)

1004: Hard - Unknown

2000: Hard - General hard bounce

2001: Hard - Recipient email does not exist

2002: Hard - Domain name does not exist

2004: Hard - Closed email account


Technical bounces occur when the email server rejects the Email due to technical errors. Reasons could be network error, SPF, DMARC or DKIM authentication error.

APSIS One responds to technical bounces just the same as with soft bounces: APSIS One continues to try to deliver the Email every hour for up to 48 hours. If the Email is still not delivered, the Profile is not affected and will still be included in future sendings.

However, if you have a large amount of technical bounces, we recommend that you contact support.

Technical bounce reasons (codes)

4000: Technical - General error

4003: Technical - Network error

4007: Technical - SPF authentication error

4008: Technical - DMARC authentication error

4009: Technical - DKIM authentication error

High Bounce rate

Monitoring bounce rates and spam complaints is an important part of sending emails to APSIS One Profiles. You can easily do this with the Email Report once your email activity has been sent, by checking periodically during the course of 2 or 3 days.

Of course, preventing bounces is just as important as taking measures after noticing a high bounce rate.

A bounce rate of less than 5% is considered normal, and as long as you're actively and periodically taking steps to prevent bounces, there is no need to worry.

However, if your bounce rates are...

5% or Higher

10% or Higher

A bounce rate of 5% and up is a concern. We recommend you to review the Email Reports of the last few Emails you've sent.

Then, look at the tasks described below on how to prevent bounces.

If you notice a lot of hard or technical bounces, we suggest you contact Support.

A bounce rate of 10% and up is considered a bad sending. There could be something wrong with the email addresses you've sent to, or a problem with your Email Authentication setup.

We recommend that you contact Support for us to help you as soon as possible.

How to Prevent Bounces

Here's what you can do to help prevent bounces.

Clean up inactive profiles

Identify inactive profiles and unsubscribe or delete them. You can create segments for these Profiles and exclude them from receiving your emails. Profiles that match a segment can also be exported in order to unsubscribe or delete them via the File Import Wizard.

Re-engage your inactive profiles

You can for example create a Marketing Automation flow to re-engage your inactive profiles. If they don't respond positively, you can confidently exclude or remove them from your Audience.

Ask your Profiles to whitelist you

You may include a message in your Welcome emails, especially to address the cases in which the Email may wrongfully land in the spam folder.

Keep track of bounces and spam complaints

And do not send to Profiles who bounced, unsubscribed or reported your emails as spam.

Use the File Import Wizard sensibly

Make sure that all addresses are real and provided with consent.


  • Do not re-subscribe Profiles that have unsubscribed unless you've received explicit, informed consent.

  • Do not import files with email addresses or any contact information that was provided by a third party.

  • Under any circumstance, do not harvest email addresses from websites, buy or rent email lists. It is very difficult, if not impossible, for you to prove that the individuals provided their consent to email communications, and even more so specifically to your brand's communications.

    Also, it goes against Efficy's terms of service since it will result in serious consequences including our servers being blacklisted and hurting its sender reputation (whether a sender can be trusted or not).

Spam Complaints

Spam or spamming refers to the action of sending bulk email messages for marketing or advertising purposes without the recipients' request or consent. Spam complaints in your Email Reports reflects only the number of Profiles who reported an Email as spam.

Thus, this number does not reflect the full number of emails that landed in a spam or junk folder. The reason that emails sometimes arrive to a spam or junk folder is usually previous spam complaints, technical reasons and the reputation of the sender. Your sender reputation can be greatly affected by consistently sending to spam traps.

Spam traps are email addresses created to identify spam. Since they don't belong to a real individual, sending to a spam trap email address means that you obtained the address without consent.

Spam traps can be tricky to deal with, but sending to them greatly increases your chances of getting emails stuck in a spam or junk folder. There are three types of spam traps:

  • Pure spam traps - created artificially to lure spammers and have never been associated to a real individual.

  • Recycled email addresses - emails that once belonged to an individual but they have been abandoned for so long that the email provider has repurposed it as a spam trap. If you happen to send to a recycled spam trap, it shows that you have failed to keep your profiles up to date and haven't cleaned up inactive profiles.

  • Invalid email addresses, which may be invalid either due to a typo or that an individual purposely provided a fake email address.

How to prevent Spam complaints

As long as you maintain a steady sending schedule, steady frequency and a good data hygiene - spam complaints should stay low.

However, you might want to ensure:

With authentication in place and knowledge about how to keep deliverability high, you minimise risk for spam complaints.


A blacklist in email deliverability refers to a list of servers or domains that have been identified as spammers. The qualifying factor is usually sending bulk emails to spam traps. There are different types of blacklists, some of them more severe than others.

This is how blacklisting affects email messages:

  1. Recipient servers have policies on whether they'll accept, flag or reject email messages from senders listed in a blacklist.

  2. The blacklist has no control over what action is taken, it merely provides the recipient server with the information about the sender. Recipient servers will "ask" the blacklist whether the sender is or isn't listed. If it isn't, the email reaches the recipient.

  3. In the case that the sender is in the blacklist, the recipient flags the email (causing it to land in the spam or junk folder), or rejects it altogether. This depends on the recipient's policies and at times they may even allow the blacklisted sender's email to go through without a problem.

  4. Some blacklists will list spamming sender domains for a long period of time, while others will only keep them for 4 or 5 hours. This depends on each particular blacklist, and recipient servers will often decide which blacklists they'll refer to in order to safeguard their users.

So, the key takeaway is that all of your deliverability efforts count when it comes to blacklisting. As long as you're taking care of your APSIS One Profiles, and avoiding spam traps, there should be no surprises.

However, if for any reason your emails were to be rejected due to a blacklist, know that our Deliverability professionals are constantly on the lookout for these events and will take action in order to identify what has happened, why the server was listed and what actions should be taken. For any blacklisting concerns, don't hesitate to contact Support.

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