When an email sent through your program cannot be successfully delivered, it may result in a bounce. Depending on the type of bounce, the user may be automatically unsubscribed to prevent repeated delivery failures.
This article explains how bounced emails are handled in Firstup, how to identify affected users, and what steps to take to resolve the underlying issue.
Understanding Bounces and Unsubscribes
A bounce occurs when an email cannot be delivered to the recipient’s inbox.
There are two main types:
Soft bounce — Temporary issue (for example, a full inbox or short-term server problem).
These do not cause an automatic unsubscribe, and future email deliveries will be attempted.Hard bounce — Permanent issue (for example, invalid email address, domain not found, or the receiving server rejected the message).
When a hard bounce occurs, the user is automatically and permanently unsubscribed from future emails.
To re-enable email delivery for that user, the address must be manually resubscribed using the Single User Resubscribe option.
Where to See Bounced or Unsubscribed Emails
You can identify bounced or unsubscribed users in several places within Firstup reporting.
Campaign Results – Email tab
View overall email delivery metrics for a specific campaign.
Last Error, shows information if the user could not receive an email due to an error.
Subscription Status, shows Unsubscribed if the user did not receive an email because they are unsubscribed.
Campaign Delivery report
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Shows campaign and user-level delivery results for a specific campaign, including:
Email Errors, emails that could not be delivered due to an error.
Unsubscribed Users List report
Shows a program-wide list of all unsubscribed users, regardless of campaign.
If unavailable, contact Firstup Support to enable it.
Includes Unsubscribe Type and Unsubscribe Date, showing whether the user unsubscribed manually, was unsubscribed due to a bounce, or was removed by an admin.
Includes Unsubscribed Count (New Metric February 2026), which tracks the number of times a user has been automatically unsubscribed due to email delivery failures (e.g. hard bounces).
User Profile
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When opening a user's profile from People | Users, the Channels section shows whether the individual's Email status is Subscribed or Unsubscribed.
If Unsubscribed, this will also show the reason that the user is unsubscribed.
How to Read the Unsubscribed Users List Report
Each unsubscribed user entry includes details about how and why the unsubscribe occurred.
Unsubscribe types
Unsubscribe Types Explained:
Admin Override — The user was manually unsubscribed by Firstup. This may have been a customer request, or this may have been done to prevent attempts to deliver to a known unreachable email address.
Bounce — The user was unsubscribed due to a permanent delivery failure (hard bounce). A bounce error message will appear in the report.
Unsubscribe Link — The user clicked the unsubscribe link in an email footer.
Unsubscribed Count
The unsubscribes count reflects how many times an individual email address has been unsubscribed over time.
- A single unsubscribe may indicate a temporary issue or one-off bounce.
- A high unsubscribe count may suggest a persistent problem with email reachability (e.g., email server configuration, corporate firewall rules, mailbox issues, or invalid domain).
Reporting on unsubscribe count helps you identify users who may require support or investigation by your IT team rather than a one-off resubscribe request.
Common bounce errors
Examples of common bounce messages* and their meanings:
550 5.1.1 User unknown — The recipient’s email address does not exist.
554 5.7.1 Message rejected as spam — The receiving mail server blocked the message as potential spam.
550 5.4.1 Relay access denied — The recipient’s domain rejected the message due to relay restrictions.
DNS lookup failure — The email domain could not be found (may indicate a configuration or DNS issue).
*These are common examples, not an exhaustive list.
Next Steps: Resolving Bounces
Since hard bounces originate from the customer’s email server or domain configuration, they cannot be fixed directly in Firstup.
To resolve them:
Review the bounce error in the report for details about the failure.
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Engage your IT or email administration team to investigate the underlying cause:
Verify the user’s email address is correct and active.
Check for mail filtering, firewall, or spam policy restrictions.
Ensure that Emails from Firstup are Allowlisted.
Once the issue is resolved, perform a Single User Resubscribe for individuals, or contact Firstup Support to request a bulk resubscribe of some or all users.
Once resubscribed, the user will again be eligible to receive email campaigns
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