> ## Documentation Index > Fetch the complete documentation index at: https://docs.unifygtm.com/llms.txt > Use this file to discover all available pages before exploring further. # Sequence enrollments > Understand how Sequence enrollments work. ## Overview A Sequence enrollment is the record of a person moving through a Sequence. Enrollments track which Sequence the person is in, which mailbox is sending, which steps have run, and why the enrollment is active, blocked, or finished. People can enter a Sequence in a few ways: * A [Play](/reference/plays/overview) enrolls the person automatically with a Sequence action * A user manually adds the person to a Sequence, such as from the person details screen, a list, or the browser extension Each enrollment uses a sending mailbox or mailbox group. If Unify cannot safely continue the enrollment, it will stop or block the enrollment instead of sending an incomplete or risky message. ## Manually add a person to a Sequence To manually add a person to a Sequence, follow these steps: 1. Open the person in Unify. 2. Click **Sequence**. 3. Select the Sequence to enroll the person into. 4. Select the mailbox or mailbox group that should send the emails. 5. Click **Add to Sequence**. If the person is already in an active Sequence, you will need to unenroll them first before you can add them to a different Sequence. A person with a recent enrollment may also be blocked from enrollment depending on your re-enrollment settings. Certain conditions may prohibit enrollment. If the person meets any exclusion criteria that apply to Sequences, you will see a warning and need to confirm before enrolling them. Lastly, if the person has opted out of emails or has a "Do Not Email" status, new enrollments will be prohibited. ## Unenroll a person from a Sequence A person who is actively enrolled in a Sequence can be removed by *unenrolling* them. This stops the active enrollment but preserves the historical enrollment information so you can still see what happened. After removal, the enrollment appears as either **Canceled** or as a completed enrollment with an unenrolled reason, depending on where the person was in the Sequence when they were removed. ## Re-enrollment rules Unify prevents a person from being in multiple active Sequences at the same time. A previous enrollment can also prevent a new enrollment, depending on your organization's Sequence re-enrollment settings. If re-enrollment is not enabled, a person who completed at least one step in a previous Sequence cannot be enrolled again. If re-enrollment is enabled, admins can configure whether people can be re-enrolled into Sequences after a waiting period and whether they can be re-enrolled into the same Sequence. When an enrollment fails because the person was already enrolled or recently enrolled, review the active or previous enrollment before changing the re-enrollment setting. The earlier enrollment may explain whether the person already replied, opted out, bounced, or was removed. ## Enrollment statuses Sequence enrollment statuses are user-facing labels that appear in Sequence analytics, enrollment tables, person timelines, and related CRM sync fields. | Status | What it means | | ------------------ | ----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | | **In progress** | A summary status for enrollments that are still active. Active enrollments can also appear as Queued, Started, Blocked, or Paused. | | **Queued** | The enrollment has been accepted, but no step has completed yet. It may be waiting for the first step, a send window, or mailbox capacity. | | **Started** | At least one step has completed successfully and the Sequence may still have additional steps to run. | | **Blocked** | The enrollment cannot continue until a user fixes an issue. Common causes include missing or invalid template variables, a paused mailbox, or a mailbox that needs reauthorization. | | **Paused** | The enrollment is paused and will not continue until it is resumed. | | **Finished** | The enrollment has ended and no more Sequence steps will run. This is a broad finished status used when a more specific finished reason is not shown. | | **Completed** | The Sequence has completed after at least one step ran. The enrollment details may show additional context, such as Replied, Opt-out, Canceled, or Excluded. | | **Bounced** | An email sent by the Sequence bounced. | | **Bounce stopped** | Unify automatically stopped the enrollment because the email address had a high bounce risk or was identified as invalid before sending. | | **Canceled** | A user removed or unenrolled the person from the Sequence before it completed. | | **Excluded** | The person matched exclusion criteria that apply to Sequences, so Unify stopped the enrollment. | ## Blocked enrollments Blocked enrollments are still active, but Unify will not continue them until the blocking issue is fixed. This prevents Unify from sending an email with missing personalization, an invalid value, or a mailbox problem. Common blocked reasons include: * **Missing variables**: the email uses a template variable that has no value for the person or company. * **Invalid variables**: a variable exists but cannot be used in the email as written. * **Mailbox paused**: the selected mailbox is paused. * **Mailbox unauthorized**: the mailbox needs to be reauthorized. * **Other mailbox issues**: Unify cannot currently send from the selected mailbox. To resolve a blocked enrollment, open the enrollment details. If the issue is a missing or invalid variable, edit the email, replace the highlighted value, and save. If the issue is a paused or unauthorized mailbox, go to mailbox settings and unpause or reauthorize the mailbox. Once the issue is fixed, Unify automatically unblocks and reschedules the step. For more detail on missing personalization, see [Template variables](/reference/sequences/personalization/template-variables#enrollment-blocking). ## Enrollment failure reasons A person can only have one active Sequence enrollment at a time. Remove the active enrollment or wait for it to finish before enrolling the person again. The person has an existing Sequence enrollment that blocks this enrollment. Open the person record to inspect the current Sequence. Re-enrollment in the same Sequence is not allowed for this person under the current re-enrollment settings. Review the previous enrollment and the re-enrollment rules. Your re-enrollment waiting period has not elapsed. Wait until the configured period passes or update the Sequence re-enrollment settings if the person should be eligible sooner. The person or their company matches an exclusion that applies to Sequences. Review the relevant exclusion before enrolling them. The person cannot be enrolled in email outreach while opted out. Review the person's consent and email preference data. The person is marked *Do Not Email* or otherwise blocked from email outreach. Update the source data only if that status is incorrect. Publish the Sequence before enrolling people into it. Choose a valid mailbox or mailbox group. If the mailbox was removed or disconnected, select another sender. Open the blocked enrollment, edit the email, replace the highlighted values, and save. Unpause the mailbox from mailbox settings. The enrollment resumes automatically after the mailbox can send. Reauthorize the mailbox from mailbox settings. The enrollment resumes automatically after authorization succeeds. Review or replace the person's email address before trying to enroll them again. Wait a moment and try again. Unify may still be finishing the previous unenrollment process.