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As a user, you cannot control bounces, but it is important that you gain an understanding of what bounces are, how a subscriber's email address becomes "bounced",and how the application deals with those bounces.

What is an email Bounce?

Bounces are messages that ISPs send back to Critical Impact to explain why they can't deliver your email to the email address you sent it to. Once you send an email, the recipient's email server either accepts your message, or "bounces" it. If the recipient's email server accepts your message, the recipient's email address remains active in Critical Impact. If the recipient's email server rejects your message, we consider this a bounce. There are two kinds of bounces - one is temporary, and one is permanent.  We'll explain how each of those work in the next section.

The Soft Bounce (temporary bounce) - The email address is valid, but the message couldn't be delivered to it, most likely due to a temporary encumbrance.

A soft bounce occurs when the recipient's email server rejects your email message due to a temporary condition that exists on the receiver's side, e.g. perhaps their inbox is full and not accepting any new messages. When a soft bounce occurs, Critical Impact will retry sending your email to the intended recipient every 60 minutes for 24 hours, which totals 24 attempts. Only after the system makes the 24 attempts does a 'bounce' appear in your tracking report. 

The 24 re-tries do not count as bounces or additional sent emails.  Instead, 24 unsuccessful retries equate to one soft bounce. The following table describes the possible causes of a soft bounce.

It is important to note that soft bounces are not controlled by our system or by you, our customer.  Soft bounces are entirely dictated by the intended recipient's email servers.

Cause

Definition

Possible Cautions and Resolutions

Inactive Email  Account

Address is temporarily unavailable as recipient's mailbox is inactive or temporarily disabled

The subscriber's email account is temporarily inactive or disabled. Mailboxes can be disabled for several reasons, including infrequent use, change of address, delinquency or dispute. These errors could be temporary or permanent. Recommended actions include sending messages to these subscribers in the short term to monitor acceptance, and then to contact the subscriber through other methods to confirm address, if delivery issues persist.
Temporary Domain FailureTemporary failure at the receiving domain   The subscriber's mailbox is not currently accepting messages. This is a temporary deliverability issue that should be resolved prior to future sends. Continue to monitor deliverability for this subscriber. Consider contacting this subscriber through alternative means if these deliverability issues persist.
OtherMailbox temporarily unavailable or indecipherable bounce message received   The subscriber's mailbox is not currently accepting messages. This is a temporary deliverability issue that should be resolved prior to future sends. Continue to monitor deliverability for this subscriber. Consider contacting this subscriber through alternative means if these deliverability issues persist.
Mailbox Full

Recipient's mailbox is full or has exceeded storage allocation 

Your recipient's mailbox is full or it has exceeded it's storage allocation. The could be caused by infrequent use, a temporary change in email checking habits, or an address change. Mailbox full errors should serve as a warning sign. Consider contacting the subscriber through alternative means to confirm that you are mailing to a valid and frequently checked address.

  
Soft Bounces can also be caused by poor sender reputation and/or issues stemming from too many bounces, too many complaints, or sending SPAM.  This type of soft bounce is called a "block bounce".  It occurs when the email server rejects your message due to filtering issues, such as URL blocks, complaints, lack of proper authentication, or the domain or IP address is found on a blacklist utilized by the receiving domain. A subscriber who receives a block bounce will be re-tried in the next email send.   The following table describes the causes of a block bounce.

Cause                     
Definition
Complaint              Your email is blocked due to complaints
Blacklist                IP address is on a blacklist
Content                  Message was filtered due to content

URL Block 

Emails containing your URLs are blocked
Authentication        Message lacks required authentication

 

Soft bounces can also be caused by technical issues. This flavor of soft bounce, also called a technical bounce, occurs when the recipient's email server rejects your message due to technical errors, such as a data format or network errors. When a subscriber experiences a technical bounce they will be re-tried in the next email send. The following table describes the causes of a technical bounce.

Cause    
Definition
Server Too BusyReceiving email server is temporarily overwhelmed with delivery attempts from you and other senders
Data Format ErrorEmail is rejected due to formatting or line length errors

Network Error

Connection lost or timed our during delivery line length errors



The Hard Bounce
    
A hard bounce occurs when the email server rejects your message due to permanent conditions (this typically results when an email address no longer exists, or is inactive). No more attempts are made to send this email campaign to this subscriber, and the subscriber will be automatically unsubscribed from all future email attempts.  While this model suits most cases, certain ISPs change from time-to-time based on how they handle spam and a number of other deliverability items.


The following table describes the possible causes of a hard bounce.

Cause

Definition

Possible Cautions and Resolutions
Domain UnknownDomain is bad or non-existentSending to unknown domains is a result of poor data capture methods, old data, or questionable data sources. Sending to old lists can also increase the likelihood of mailing to dead domains, as domains that are no longer active will be represented on old lists. To avoid receiving a high number of "Domain Unknown" errors, we recommend sending a test send to 10% of your regular mailing volume. In doing so, you can assess the results from the test send without exceeding the acceptable bounce and complain rates and make a reasonable risk assessment before proceeding with a larger send.
User UnknownAddress is invalid and/or failure is permanent per bounce messageIndustry statistics indicate that up to 33% of email addresses become invalid over a 12 month period. Receiving the User Unknown error indicates that the address is no longer active or has never been an active email address. Because of the high rate of turnover of email addresses, sending to subscribers on a regular basis will decrease the possibility of a sudden spike on a specific campaign. If mailing to an old subscriber list, we recommend sending a random 10% test to avoid a sudden increase in bounces. This error could also be the result of poor data capture methods. If this is the case, we recommend requiring subscribers to enter their email address twice

Bad Address Syntax  

 

Email address invalid  

 

The email is not in a correct syntax. For example, you may have left out the "@" symbol or didn't include a domain name (like "yourdomaincom" instead of "yourdomain.com"). Check your email address syntax and correct any errors you see.

High Unknown Address Percentage 

 

Email is blocked due to the high quantity/percentage of unknown or inactive addresses on your list   

The subscriber's ISP has flagged your IP address for sending too many messages that were unknown or inactive. The ISP sees that you sent emails to people that didn't accept them. To improve this, see the section on Best Practices.

 

 

Other    

 

Address is invalid and/or failure is permanent per bounce message   

 

 

   
Bounce Tracking

We track your bounces in the tracking area of the application. To access your bounce tracking data, follow these steps:

  1. Click the Reports folder.
  2. Click Custom Reports.
  3. Select Display All Hard and Soft Bounces by Date.
  4. Click Run Report

We take bounces very seriously. Poor deliverability from any of our customers damages the reputation of the company and, by extension, all of our customers. Therefore, the Sending Guidelines and Thresholds are in place to prevent abuse of our email system and to ensure our clients practice permission-based, opt-in email. We continue to lead the industry in deliverability rates - due in part to our commitment to, enforcement of, and client consultation on permission marketing best practices.

 

 

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