Understanding email bounces

A bounced email is one that could not be delivered to its intended recipient. Although Dynamics 365 Marketing recognizes several individual bounce categories, they generally fall into two groups: hard bounces and soft bounces. Understanding the difference can help you determine whether you need to correct contact data, adjust your email practices, or investigate a problem outside your organization.

Hard bounces

A hard bounce usually indicates a permanent problem with a specific recipient's email address. Common hard-bounce causes include:

• Invalid mailbox: The recipient's email address may contain a typo or the mailbox may not exist.
• Invalid domain: The domain may be misspelled, incorrect, or inactive. For example, you may be sending to name@company.com when the correct address ends in .org.
• Inactive mailbox: The mailbox may no longer exist. In B2B marketing, this commonly happens when someone leaves their employer and their email account is deactivated.

Start by checking the email address and domain for obvious errors. If the address is correct but continues to hard bounce, there may not be much you can do to restore it. Consider placing these contacts on a suppression list, excluding them from future marketing segments, or deactivating the contact when appropriate. Continuing to send messages to invalid addresses can eventually affect your sender reputation.

Soft bounces

Soft bounces are more complicated because they can be related to the content or sender of an email as well as the recipient's email server, security configuration, or routing. Potential causes include:

• A full mailbox.
• DMARC or domain authentication problems.
• Sender reputation issues.
• Greylisting.
• Recipient server errors.
• Routing errors.
• Recipient security policies.
• Previous bounce activity.
• Spam-related concerns.

Some soft bounces can be addressed by changing your content or sending practices, while others require action from the recipient or their organization's IT team.

Full mailboxes

A message may bounce because the recipient does not have enough available mailbox storage to receive new email. A full mailbox can be temporary. However, it may also indicate that the inbox has been abandoned. If the same address repeatedly generates this error, consider whether the contact should remain in your mailing lists.

DMARC and sender authentication

DMARC is an email authentication mechanism designed to help prevent spoofing, where a malicious or misleading email appears to come from a legitimate sender. If you encounter authentication-related bounces, confirm that the From and Reply-to information configured for your marketing email is appropriate for the domain associated with your marketing environment. Using free email services such as Gmail or Yahoo to distribute mass marketing email instead of a private domain can also create authentication and reputation concerns.

Sender reputation issues

Repeated problems with your email content, sending domain, IP address, or sending volume can damage your sender reputation. Spam filters may begin catching more of your messages, which can lead to lower deliverability and additional bounces. If you notice repeated reputation-related errors, review:

• The quality of your email content.
• Your sending domain and authentication.
• Your mailing list quality.
• How frequently you send emails.
• Whether you're exceeding sending limits.

Don't ignore a pattern of reputation-related failures. It may indicate a broader problem affecting future campaigns.

Greylisting and server errors

Greylisting can occur when a recipient receives email from a domain or IP address for the first time. Their server may temporarily reject the message so the new sender can be reviewed. Other temporary failures can result from overloaded recipient servers or technical problems that prevent delivery. Routing errors are another possibility. These occur when the recipient's server is unable to properly relay your message to the correct mailbox.

Recipient security policies

An organization's internal security policies may restrict or completely block emails from outside senders or particular groups. In these situations, you may need to contact the recipient through another channel and ask them to work with their organization to add your sending domain, IP address, or email address to a safe-sender list.

Using suppression lists

If a recipient is on a suppression list, Dynamics 365 will prevent the email from being delivered to that contact. Unlike problematic delivery attempts, suppressing contacts does not negatively affect your sender reputation. When an address consistently presents delivery problems and cannot reasonably be corrected, excluding it from future sends can help protect the overall health of your email program.

Build healthier marketing segments

Good segment management can help reduce delivery problems before you send an email. When creating marketing segments, check important contact information such as:

• The contact is active.
• The email address field contains data.
• The contact is permitted to receive bulk or promotional emails from you.

Regularly review your audiences so your segments do not become filled with outdated, invalid, or disengaged contacts.

Optimize your email content

Content and design can also influence deliverability. Avoid patterns commonly associated with phishing and spam, such as:

• Excessive punctuation.
• Frequent use of ALL CAPS.
• Poor spelling and grammar.
• Excessive urgency.
• Unrealistic or exaggerated promises.
• Overuse of phrases such as "Act now," "Don't wait," "You've won," or "100% satisfaction guaranteed."

Using this type of language occasionally does not automatically make an email spam. However, consistently combining questionable content with a poor sender reputation or unhealthy mailing list can increase the likelihood of your messages being filtered.

Keep email design clean and accessible

Other email practices can help support deliverability and provide recipients with a better experience:

• Reduce unnecessary file sizes, graphics, and other visual content that may make messages slower to load.
• Include a plain-text alternative to your designed HTML email.
• Use a clear and specific call to action.
• Avoid overwhelming recipients with too many calls to action.
• Keep mobile users in mind and make layouts easy to read on smaller screens.
• Make it easy for recipients to unsubscribe.
• Respect subscription and consent preferences promptly.
• Consider double opt-in to help ensure you're sending to people who genuinely want your messages.

Dynamics 365 can automatically generate a plain-text alternative for your marketing emails, helping you avoid one common issue evaluated by spam filters.

Analyze bounces after sending

After an email campaign runs, use Dynamics 365's analytics to understand what happened. In Outbound Marketing, open the email and navigate to the Insights tab. Under Delivery, you can review metrics such as:

• Total emails sent.
• Total emails delivered.
• Blocked messages.
• Delivery failures.

The Blocked area generally includes issues related to consent or suppression. The Delivery failed area contains hard and soft bounces. When you open a bounce category, you can review information including the contact, email address, bounce category, bounce reason, and timestamp. You can also export the list to Excel for easier filtering and analysis.

Look for patterns by domain

Dynamics 365 also lets you examine delivery results by recipient domain. This can be especially helpful when a large number of failures are associated with one organization or domain. Instead of treating each bounce as an isolated event, you may discover a larger security, routing, or configuration problem that can be addressed at the organization level.

Review insights in Real-Time Marketing

In Real-Time Marketing, you can access similar delivery information from the Reports area of the email record. The Delivery panel provides access to more detailed information about delivered, blocked, and failed email sends. Email reporting can also aggregate information across the journeys in which an email was used, while allowing you to narrow your analysis to individual journeys when necessary. You can also review marketing insights at the individual contact or lead level to better understand that person's interaction history and use those insights to inform future outreach.

Turn bounce data into action

Some email bounces are unavoidable. What matters is identifying patterns and responding appropriately. Correct invalid data when possible, stop repeatedly sending to addresses that cannot receive your messages, maintain healthy and permission-based audiences, monitor sender reputation, and regularly review your delivery analytics. By treating bounce data as an opportunity to improve your email strategy, you can maintain cleaner marketing lists, address recurring deliverability problems, and improve the effectiveness of future campaigns.