Check out the video explaining bounces below:
A “bounced e-mail” (or simply “bounce”) is a message that cannot be delivered to its destination. Usually, Internet Service Providers (ISPs) will return the e-mail to the sender along with some information indicating why the message could not be delivered.
The different kinds of bounces can be grouped depending on whether the fault lies with the sender, the receiver, or somewhere in between. When it handles bounces due to problems with the recipient, it may invalidate the recipient’s e-mail address. This cleans mailing lists and segments by preventing any future mailings from being sent to that recipient. This is an important step in maintaining a good sender reputation.
When Symplify handles bounces due to problems with the sender or problems in transit, it takes no automatic action. For all bounces, regardless of type, it records as much information as possible for reporting.
Hard bounce vs Soft bounce
A hard bounce is a recipient problem that is permanent and is not expected to clear up. The classic cause of a hard bounce is a destination address that does not exist due to a typo or account termination. When Symplify encounters a hard bounce, it immediately invalidates the contact’s e-mail address to prevent further mailings from being sent.
A soft bounce is a recipient problem that is temporary and may clear up at some point in the future. The classic cause of a soft bounce is a full mailbox – the message cannot be delivered now, but in the near future it is possible that either the storage quota will be lifted or the mailbox will be cleared out. You will still be able to send to addresses that soft bounced.
Five Soft bounces
If an email address gets five soft bounces in a row, Symplify will mark the address as unsubscribed and will not send any more emails to that address. This is primarily to avoid increased deliverability problems, which occur when you keep sending emails to recipients that repeatedly report soft bounces. The main reason is that the receiving server may be incorrectly categorizing a hard bounce as a soft bounce.
When do Symplify stop sending to bounced addresses?
- Hard Bounce: Symplify immediately invalidates the contact’s email address.
- Soft Bounce: After five consecutive soft bounces, Symplify marks the address as unsubscribed and stops sending emails to it.
How do I prevent future bounces?
- Make sure to check bounce statistics for all emails as often as you check the open rate.
- Use Google’s reCaptcha
- Sending a “Welcome” or “Confirmation” message from a separate IP space allows for bounce processing of invalid addresses and ensures that high unknown user rates for new subscribers do not impact performance of regular email campaigns sent from different IPs.
- On sign-up pages, ask customers to type in the email address twice to prevent “fat fingering” mistakes which could unintentionally result in an address that does not exist.
When receiving subscriptions from third party partners, affiliates, or list services:
- Test a sample of the file from a separate IP space and monitor unknown user rates before adding the file to the database.
- Review the partner data file to ensure that malformed, role account and nonsensical email addresses are removed.
- Mail partners’ data from a separate IP space to monitor their ongoing data quality and unknown-user rates.
- Regularly audit partners’ sign-up processes to ensure they meet industry best practices for address collection.
- Establish an ongoing process for actively removing subscribers that are both old and inactive.
Bounce categories
There are hundreds of different bounce types and it often seems that depending on the ISP they have different messages they send back to Symplify for us to understand why the email bounced. To make it easier for you as a user to understand why your email bounced, we group them into different categories. Read about the most common ones below.
Hard bounced categories
Bad Domain
Explanation:
The domain does not exist (i.e. someone@hoo1ootmail.com).
How to fix the problem:
You need to look at your opt-in procedures and be sure that people are signing up with the correct email address. Consider double opt-in or asking the recipient to write their email address twice so you are sure they input the correct address.
Bad Mailbox
Explanation:
The email address does not exist (anymore).
How to fix the problem:
You need to look at your opt-in procedures and be sure that people are signing up with the correct email address. Consider double opt-in or asking the recipient to write their email address twice so you are sure their input the correct address. Bad mailbox often comes from sending to old email addresses. Email addresses get stale after 3 months. This type of bounce will get you into deliverability problems so make sure you don’t get many of these.
Bad Email address
Explanation:
A bad email address means there is something wrong with the address. It is often incomplete or misspelled.
How to fix the problem:
You need to review the email addresses on your list and check that they are complete. You can export the ‘Hard bounces’ from the send-out to more easily identify which addresses are affected.
Inactive Mailbox
Explanation:
The email address has been disabled and is no longer accepting messages.
How to fix the problem:
Review your opt-in procedures to ensure people are signing up with the correct email address. Consider using double opt-in or asking recipients to enter their email address twice to ensure they input it correctly.
No Answer from Host
Explanation:
A technical bounce, similar to “No one is answering the phone.” We tried to deliver the email several times, but the receiving server did not respond. You should consider the email address as non-existent
Relaying Issues
Explanation:
A technical bounce.
Routing Error
Explanation:
A technical bounce. The problem does not lie with the sender or the recipient, but somewhere in between. Normally this means that the email is passing through different servers but suddenly stops because it does not know where to go next. Often seen when groups of addresses has been removed or subdomains does not exist anymore.
You should consider the email address as non-existent.
Soft bounced categories
Message Expired
Explanation:
The email is too old to be delivered. Every email has a timestamp that determines when it is considered too old to be sent. If the receiving server temporarily rejects the email and asks Symplify to retry, Symplify will attempt delivery multiple times each hour for several days until the email expires. This issue can sometimes be caused by sudden changes in your send-out volume.
How to fix the problem:
This problem usually won’t fix itself, and you might not see it with every email. Please contact support for assistance.
Bad Connection
Explanation:
Symplify can’t connect with recipient server. Tried several times.
How to fix the problem:
Check for the same problem in your next email send-out. If the issue does not recur, it was likely a temporary problem on the recipient’s server. If it continues to bounce after several attempts, you can contact support for testing, although we may not be able to resolve it since the issue is usually on the recipient's server.
Quota Issues
Explanation:
Recipient mailbox is full. Mailbox does not accept any more emails at the moment.
How to fix the problem:
The problem will resolve if the recipient deletes some emails from their inbox. If this does not happen, you may want to ask the recipient to provide a different email address or unsubscribe them from your lists.
Content Related
Explanation:
The email bounced due to issues in its content. This includes not only the HTML but also the message headers. Common causes include URLs in the email that have a poor domain reputation or other content-related problems.
How to fix the problem:
Test your emails a lot. Change the content and see if it then reaches the inbox. There are different tools online you can try for this. Symplify also provide different services for these types of investigations. Please contact your Customer Success Manager for more info.
Spam Related
Explanation:
Recipients server thinks your emails are spam. This can happen for several reasons, such as high bounce rates, too many spam complaints, or content that triggers spam filters. It often occurs when the recipient’s server has seen multiple issues with your previous emails.
How to fix the problem:
Test your emails a lot. Change the content and see if it then reaches the inbox. There are different tools online you can try for this. Symplify also provide different services for these types of investigations. Please contact your Customer Success Manager for more info.
Policy Related
Explanation:
You are not allowed to send emails to the recipients server.
How to fix the problem:
You need to contact the ISP/domain owner and politely ask them to open up for emails coming from the following IP addresses: 81.201.223.0/24, 192.165.55.0/24 and 184.107.113.0/24
Invalid Sender
Explanation:
There may be technical issues on your side as the sender.
How to fix the problem:
Symplify Support is able to check for possible reasons.
Other
Explanation:
The recipient’s server does not provide a reason for the email bounce.
How to fix the problem:
Follow up on the next emails to see if the problem disappears. If not, this is likely a very difficult issue to resolve since the reason for the bounce is unknown.