Marketing Cloud Next - Email Bounce Management

Note: this applies to Marketing Cloud Next (Growth/Advanced) as well as the Marketing App for Salesforce Foundations, Salesforce Pro Suite, Salesforce Starter. 

Marketing Cloud Next is designed to effectively monitor and manage email bounces, which are crucial for maintaining a healthy sender reputation and ensuring successful email delivery. Bounces are messages that inbox/mailbox providers (ISPs) send back to explain why they can’t deliver your email. When an email can’t be successfully delivered, the Marketing Cloud Next will log a BOUNCE row in the Email Engagement DMO and potentially prevent future email sends depending on the type of bounce. Note that there should only ever be one BOUNCE row in the Email Engagement DMO per attempt send email even if the email is retried (if for example a soft bounce is received, the email servers will retry the email). 

May 2026 Bounce Management Update

Prior to late May 2026, bounces were categorized as either Soft or Hard bounces. After May 2026, Marketing Cloud Next has added a few additional categories (Block and Technical) to provide a more nuanced handling of email bounces. Bounces that occurred prior to this change will not be updated with the new categories. You may see a shift in the Soft and Hard bounce rates in any out of the box metrics as a subset of these will now be categorized as Block and Technical bounces. 

Soft Bounces (Temporary Delivery Failures)

Soft bounces indicate temporary delivery issues that may resolve on their own. The recipient address is valid but delivery failed for a transient reason.

Common Causes

• Mailbox full (recipient over storage quota)
• Mailbox temporarily inactive or suspended
• Greylisting (ISP anti-spam technique requiring retry)
• Temporary rate limiting by ISPs
• DNS lookup failures or timeouts
• Message format or size issues

System Behavior

• Not suppressed — the email address remains eligible for future sends.
• Marketing Cloud Next automatically retries sending the email over a 12-hour period.

Next Steps

Soft bounces typically require no action — the system handles automatic retries. However, if the same address soft bounces for 30+ consecutive days (especially "mailbox full"), it likely indicates an abandoned account and should be suppressed. Monitor for patterns: if soft bounce rate exceeds 10% for a specific ISP, it may indicate an ISP-side issue worth investigating.

Block Bounces (Reputation & Policy Issues)

Block bounces occur when the receiving ISP rejects your email due to authentication failures, or policy violations.

Common Causes

• Authentication failures (SPF, DKIM, or DMARC not passing)
• IP or domain listed on blocklists
• Content flagged as spam-like by ISP filters
• High complaint rates triggering proactive ISP blocking
• Recipient has marked your sender as spam previously
• Corporate email policies blocking marketing content
• Recipient explicitly blocked your sender address

System Behavior

• Not suppressed — the email address remains eligible for future sends.
• Marketing Cloud Next automatically retries sending the email over a 12-hour period if the original raw bounce response from the receiving server was a 4xx bounce. 

Next Steps

Block bounces signal reputation problems that require immediate attention. Verify domain authentication (SPF/DKIM/DMARC) in your domain settings, review ISP postmaster tools (Gmail Postmaster, Microsoft SNDS, Yahoo Postmaster), and check for blocklist listings using tools like MXToolbox. If block bounce rate exceeds 2%, investigate sender practices including list quality, send frequency, and content patterns.

Technical Bounces (Infrastructure Issues)

Technical bounces indicate problems with mail infrastructure, connectivity, or sending systems — not data quality or sender reputation issues.

Common Causes

• DNS resolution errors or timeouts
• SMTP connection failures or timeouts
• Authentication handshake errors (TLS/certificate issues)
• Protocol command errors or mismatches
• Message expiration after maximum retry attempts
• Network connectivity or routing problems

System Behavior

• Not suppressed — the email address remains eligible for future sends.
• Marketing Cloud Next automatically retries sending the email over a 12-hour period if the original raw bounce response from the receiving server was a 4xx bounce.

Next Steps

Technical bounces usually resolve automatically and require no action. They often correlate with volume spikes, IP warmup periods, or temporary ISP outages. However, if technical bounce rate exceeds 5% across multiple ISPs for more than 24 hours, or you see persistent connection errors, contact Support as this may indicate IP routing or infrastructure issues requiring investigation.

Hard Bounces (Permanent Delivery Failures)

Hard bounces indicate the recipient email address permanently cannot receive mail — the address doesn't exist, is invalid, or has been closed. These primarily stem from data quality issues.

Common Causes

• Email address doesn't exist (user unknown, mailbox not found)
• Domain doesn't exist or has no mail servers
• Email address syntax is malformed or invalid
• Account closed or deactivated by ISP
• Mailbox inactive or disabled

System Behavior

• Permanently suppressed — Marketing Cloud Next will not attempt delivery again in a future campaign.
  • You will see this not sent reason "Recipient address returned hard bounce in previous send attempt" if you attempt to send to an email address that was previously hard bounced.
• Suppression tied to email address (not individual/contact/lead/prospect record). Even if you delete the record and re-import with the same email address, that email address remains suppressed. 
• Suppression is specific to your Marketing Cloud Next account (any other Marketing Cloud Next customer can still attempt delivery). 
• In general, hard bounces should not be reset to protect your deliverability reputation.
  • If you have email addresses that return a not sent reason of "Recipient address returned hard bounce in previous send attempt" that you would like to make mailable again, please open a support case with Salesforce support and provide a CSV file with the list of email addresses. Please note that not all requests will be granted.

Next Steps

Hard bounces point to upstream data quality problems. Rising hard bounce rates indicate issues with list acquisition, data imports, or validation at point of collection. Implement email validation services (e.g. NeverBounce, ZeroBounce) for bulk list cleaning, add real-time validation to signup forms, implement double opt-in, and audit recent list sources if you see sudden spikes. 

Please note: If you need to send email to an email address that previously hard bounced, please create a support case for this request. 

Most hard bounces should not be reset to avoid impacting your email deliverability reputation. Exceptions may include:

• False positive hard bounces due to a temporary outage (this occasionally happens at major ISPs like Microsoft/Google). 
• Recipients' company has strict firewalls. These should only be reset if you've worked directly with a company to whitelist your IP/Domain.

Lead/Contact Default Bounce Fields

If you have enabled email bounce handling in CRM, you may see the fields EmailBouncedDate and EmailBouncedReason fields on the lead/contact records are populated when a CRM based email hard bounces. Note that Marketing Cloud Next does not have an out-of-the box process to populate EmailBouncedDate and EmailBouncedReason fields on lead/contact records.