In order to change a subscriber's status from Held (undeliverable) back to Active, you will first need to change their status to unsubscribed.
Once they are in a unsubscribed status, you will have the ability to change their record back to active.
Once they are in a unsubscribed status, you will have the ability to change their record back to active.
To reactivate within the application (individual subscribers):
1. Log in to the Marketing Cloud application
2. Go to Email Studio | Email | Subscribers | All Subscribers
3. Click the Search button
4. Select Email Address from the Search where: drop-down field
5. Enter the subscriber's email address in the Is equal to: field and click the Find Now button
6. Click to highlight the subscriber from the search results list and click the View Properties link
7. In the General tab, click the Unsubscribe from all button
8. Click the OK button in the dialog box
9. In the General tab, click the Activate button (activates only on the All Subscribers list)
10. To activate the subscriber on individual lists, select the List tab.
11. Select the desired list and click the Details button
12. Click the Activate button to reactivate the subscriber on the specified list
13. Click the OK button in the dialog box to exit
2. Go to Email Studio | Email | Subscribers | All Subscribers
3. Click the Search button
4. Select Email Address from the Search where: drop-down field
5. Enter the subscriber's email address in the Is equal to: field and click the Find Now button
6. Click to highlight the subscriber from the search results list and click the View Properties link
7. In the General tab, click the Unsubscribe from all button
8. Click the OK button in the dialog box
9. In the General tab, click the Activate button (activates only on the All Subscribers list)
10. To activate the subscriber on individual lists, select the List tab.
11. Select the desired list and click the Details button
12. Click the Activate button to reactivate the subscriber on the specified list
13. Click the OK button in the dialog box to exit
***NOTE: To reactivate the subscriber on other lists, repeat steps 10-12 for each list.***
To reactivate via an import (multiple subscribers):
1. Log in to the Marketing Cloud application
2. Go to Email Studio | Email | Subscribers | Lists or All Subscribers
3. Click the linked name of the list in question (if sublist)
4. Click the Search button
5. Select Subscriber Status from the Search where: drop-down field
6.Select Undeliverable from the Is equal to: drop-down field and click the Find Now button
7. Click the Export option
8. Complete the wizard to export the subscribers to a file, selecting the Email Address and Subscriber Status fields to be included in the results
9. Edit the exported file and change the Email Status field values to Unsubscribed for every subscriber on the list that needs updated
10. Perform an import to the All Subscribers list selecting either Add & Update or Update. This will change their status to unsubscribed for all lists.
11. Edit the export file again and this time change the Email Status field to Active for every subscriber on the list that needs updated
12. Perform an import to the All Subscribers list selecting either the Add & Update or Update. This will change their status to active for all lists.
13. Perform an import to any other desired lists to change the subscriber status to Active at the list level.
2. Go to Email Studio | Email | Subscribers | Lists or All Subscribers
3. Click the linked name of the list in question (if sublist)
4. Click the Search button
5. Select Subscriber Status from the Search where: drop-down field
6.Select Undeliverable from the Is equal to: drop-down field and click the Find Now button
7. Click the Export option
8. Complete the wizard to export the subscribers to a file, selecting the Email Address and Subscriber Status fields to be included in the results
9. Edit the exported file and change the Email Status field values to Unsubscribed for every subscriber on the list that needs updated
10. Perform an import to the All Subscribers list selecting either Add & Update or Update. This will change their status to unsubscribed for all lists.
11. Edit the export file again and this time change the Email Status field to Active for every subscriber on the list that needs updated
12. Perform an import to the All Subscribers list selecting either the Add & Update or Update. This will change their status to active for all lists.
13. Perform an import to any other desired lists to change the subscriber status to Active at the list level.
Source : https://help.salesforce.com/articleView?id=000268698&language=en_US&type=1
