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Marketing Cloud - Bounce Management in Email Studio

The Marketing Cloud Email Studio allows marketers to create personalised emails for marketing purposes and send them to specific segments. For a successful email campaign, the quality of your mailing list is crucial, otherwise, you are at risk of ending up on a blacklist. But even with up-to-date, carefully managed lists, it happens that emails do not reach the recipient. These errors are returned to Marketing Cloud as so-called bounces and allow you to see the reason for the sending error.

What are bounces?

Bounces are messages sent back to Marketing Cloud by an Internet Service Provider (ISP) explaining why an email could not be delivered. Subscribers who experience these bounces are marked as "Bounced". Once an email campaign has been sent, Marketing Cloud users no longer have any control over the bounces. You can only understand the reasons for a bounce and what the consequences are for future mailings.

There are two types of bounces:

Soft bounces
A soft bounce is an email that is rejected by an email server for a temporary reason. An example of this would be a full inbox.

Hard bounces
In contrast, a hard bounce is a rejection of an email for a permanent reason, such as an unknown domain.

In the following, the subscriber status and the functionality of the Marketing Cloud in dealing with bounces and the two bounce types are presented in detail.

Subscriber Status

In the Marketing Cloud, each contact has one of the following email statuses. Bounces must be seen in this context:

Active (green)

The goal is to have as many active subscribers as possible on mailing lists. Active subscribers are a sign that emails are arriving in the inbox. This means that no activity has occurred that would cause the subscriber's status to be Bounced, Undeliverable, Unsubscribed or Deleted.

Bounced / Returned (yellow) 

With this status, the email was rejected by the recipient's email server. This means that a subscriber has one or more soft or hard bounces.

Held / Undeliverable (grey)
If a subscriber has three or more soft or hard bounces and more than 15 days have passed since the first bounce, his/her status is changed to Held. Hard bounces from a trusted domain are marked as Undeliverable after the first hard bounce.

If a subscriber with the status Undeliverable (or Bounced) opens an email or clicks on a link in a sent email, the status is reset to Active.

Unsubscribed (red)
If a subscriber unsubscribes from one, several or all lists, the status for the selected or all lists is changed to Unsubscribed. The status can also be manually changed to Unsubscribed by a Marketing Cloud user in a list. If a subscriber makes a spam complaint, the subscriber status also changes to Unsubscribed for all his lists.

If a Marketing Cloud user deletes a subscriber from a specific list, the subscriber status for this list changes to Deleted. If a user deletes the subscriber from the All Subscribers list, the global status of the subscriber changes to Deleted.

Bounce management process

  • If a hard bounce from a non-trusted domain is recorded, it is treated as a soft bounce. Hard bounces from a trusted domain are marked as Undeliverable after the first hard bounce.
  • It is important to consider the time span of 15 days since the first bounce. If several emails in this period register a soft bounce or hard bounce from a non-trusted domain, subscribers will continue to receive emails. For bounces within this time, only the number of bounces will be increased. After 15 days, a check is made to see whether the number of bounces is greater than or equal to 3, and if this is the case, the subscriber's status is changed to Undeliverable.

Bounce types

1. Soft Bounce
When an email server rejects an email for a temporary reason, this results in a soft bounce. An example of this is a full inbox. In the case of a soft bounce, Marketing Cloud tries to resend the email to the subscriber every 15 minutes for 72 hours, i.e. 288 times. After this period, the subscriber's status is marked as Bounced. Once a bounce appears in the tracking, it cannot be changed.

The 288 attempts are not counted individually as a bounce, but all together as 1 unsuccessful attempt. If all 288 attempts fail, the Subscriber Status is set to Bounced. If the subscriber opens one of the 288 attempts, the status is changed to Active. This also applies to opening an old email in the Inbox.

Not all soft bounces result in 288 retries. Some soft bounces are immediate and permanent. These bounces generate a specific message:
  • mailbox would exceed maximum allowed storage
  • user account is over quota
  • mailbox is full
  • mailbox disabled
  • mailbox temporarily disabled
  • mailbox disabled, not accepting messages

After the third soft bounce of a subscriber, the status changes to Held (Undeliverable).

Reasons for soft bounces:
Definition Possible cautions and resolutions
Inactive 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. We recommend sending messages to these subscribers in the short term to monitor acceptance, and then contacting the subscriber through other methods to confirm the address.
Mailbox FullRecipient's mailbox is full or has exceeded storage allocation.Your recipient's mailbox is full or it has exceeded its storage allocation. A full mailbox is usually from infrequent use, a temporary change in email checking habits, or an address change. Mailbox full errors are a warning sign. Consider contacting the subscriber through alternative means to confirm that you're mailing to a valid and frequently checked address.
Temporary Domain FailureTemporary failure at the receiving domain.The subscriber's mailbox isn't currently accepting messages. Resolve this temporary issue before 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 isn't currently accepting messages. Resolve this temporary issue before future sends. Continue to monitor deliverability for this subscriber. Consider contacting this subscriber through alternative means if these deliverability issues persist.
2. Block Bounce

A block bounce is a subcategory of soft bounce. Block bounces occur when an email server rejects an email due to filter issues. This includes, for example, URL blocks, no clear authentication or the domain or IP address is on a blacklist. In case of a block bounce, delivery is attempted again the next time an email is sent.

Cause Definition
Complaint Your email is blocked due to complaints.
BlacklistIP address is on a blacklist.
ContentMessage was filtered due to content.
URL BlockEmails containing your URLs are blocked.
AuthentificationMessage lacks required authentication.
3. Technical bounce
A technical bounce is also a subcategory of soft bounce and occurs due to technical problems such as data format and network errors. These bounces are also retried the next time the email is sent.
Cause Definition
Server too busy Receiving 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 ErrorConnection lost or timed out during delivery line length errors.
4. Hard Bounce
A hard bounce occurs when the email server rejects an email due to persistent conditions. This bounce typically occurs when the user is unknown or the domain cannot be found. What happens next depends on the status of the subscriber.

If the status was active in advance:
If the subscriber's status was active, their status will now change to Bounced. No more attempts are made to send this email campaign to this subscriber, but the subscriber is retried in your next email campaign. In terms of bounces, each email sent is considered a campaign.

If the status was Bounced in advance:
If the subscriber's status was already Bounced, this indicates that this was not the first bounce and it is thus handled differently. If this email campaign is the first or second email campaign in which the subscriber has experienced a bounce, the subscriber will retain the status Bounced. In the next campaign, the sending will be attempted again.

However, if this email campaign is the third campaign in which the subscriber bounced, it will be checked when the first bounce message was received for this subscriber. If less than 15 days have passed since the first bounce message was received, the subscriber will retain the status Bounced and will be included again in the next campaign. No further attempts will be made for this current email campaign. If a bounce occurs more than 15 days after the first bounce message, the subscriber status changes to Held (Undeliverable).

However, there is another exception. If the hard bounce is from a trusted domain, the status changes directly to Undeliverable. Currently trusted domains are, (including all active Hotmail country domains such as and all active Road Runner domains such as

Reasons for Hard Bounces:
Cause Definition Possible Cautions and Resolutions
Domain unknown Domain is bad or non-existent. Sending 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 are 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. 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 or failure is permanent per bounce message.Industry statistics indicate that up to 33% of email addresses become invalid over 12 months. 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 turnover rate of email addresses, sending to subscribers regularly decreases 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 so, we recommend requiring subscribers to enter their email address twice.

Bad Address SyntaxEmail address invalid.The email contains incorrect syntax. For example, you left out the "@" symbol or didn't include a domain name (like "examplecom" instead of "").

Check your email address syntax and correct any errors you see.
High Unknown Address PercentageEmail is blocked due to the high quantity or percentage of unknown or inactive addresses on your list.The subscriber's ISP has flagged your IP address for sending too many messages that got blocked. The ISP sees that you sent emails to people that didn't accept them. 
OtherAddress is invalid or failure is permanent per bounce message.
Subscribers who continuously generate hard bounces should be removed from the mailing list.

5. Unsubscribed Status
Subscribers may be marked as Unsubscribed for the following reasons:

  • The subscriber clicks on an unsubscribe link in an email or chooses to unsubscribe in a preference centre.
  • The subscriber reports an email as spam to an ISP with whom Marketing Cloud has a feedback loop (AOL, Hotmail, Comcast and others).
  • The subscriber's address is manually unsubscribed by a Salesforce Marketing Cloud user.


It is absolutely essential to understand the bounce management of Marketing Cloud because it is not quite intuitive. By understanding the functionality, mailing lists can be adjusted and measures can be taken to increase or maintain a high deliverability rate. Be sure that you only send your campaigns to subscribers, who explicitly agreed to receive your emails and keep your lists up-to-date. If you have any questions about bounce management, please feel free to contact us.


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