Create a data field which is used identify potential duplicate contacts.

Create a segment to identify contacts with a mobile number stored in a custom data field.
​This is the data field you previously used in your Triggered SMS profile for sending SMS in automations.

Export this segment, and add a column to the exported file to mark these mobile numbers as potential duplicates.

Re-import the contacts, mapping only the custom mobile number data field column in the import file to the mobilenumberid field in Dotdigital, and the potential duplicates column to your POTENTIAL_DUPLICATES data field. At this step, you must not map the email column in your import file.
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The process up to this point has allowed you to identify the mobile numbers that were previously stored against email contacts in a custom data field, and imported these as mobile number only unified contacts. Any of the mobile numbers that also existed in your broadcast SMS contacts also now exist as mobile number only unified contacts, and have been marked as potential duplicates.
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This allows us to delete these mobile number duplicates, so that we can do a final data import to merge the mobile numbers we have gathered with the correct email addresses in a single unified contact record.
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To complete the process:
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Create a segment of the potential duplicates and delete these duplicates from your account. The segment must be converted into a list to allow you to monitor the progress of the deletion.

Reimport your data to create merged unified contact records.

Expand the User menu, and go to Settings > Contacts > Contact data fields, then select the Custom data fields tab.
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Select NEW DATA FIELD.

For Name, enter POTENTIAL_DUPLICATE.

Expand the Data type drop-down menu, then select Yes/No.

Expand the Default value drop-down menu, then select No.

For Access leave the value as Private.
Optionally, expand the Folder drop-down menu, then choose a folder to store your data field.

Select CREATE.

Create a segment called Contacts with a mobile number in a custom data field.
​To learn more, check out the article Create a segment.

Drag the data field block onto your segment Include area. Then select the block to open the rule settings.

Select the custom data field you have been storing mobile numbers in.
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Expand the rule drop-down menu, select Is not empty, then select OK.

Select SAVE, then GENERATE SEGMENT.

Go to Audience > Segments.

Select the Mobile number in a custom field segment.

Select Display, and ensure you select at least the Email, POTENTIAL_DUPLICATE, and custom phone number data fields. Then select APPLY.
​If you want to export a copy of all data field data you hold for these contacts, you can select Select all to include all data fields in the export file.
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Expand the Export drop-down menu, and select Export all. You don’t need to include marketing preferences.

Select CONTINUE.

On the Exports page, wait for your export to finish, then select Download. A CSV export downloads to your local computer.

On your computer, open the exported segment file in Excel.

Enter Yes in every cell in the POTENTIAL_DUPLICATE column.

Save the file to your computer.

Go to Audience > Contacts, then expand the NEW CONTACT drop-down menu and select Import contacts.

For File, select CHOOSE FILE and select the CSV file that you edited in the previous step.
Optionally, for Email address to notify, enter an email address to receive a notification when the import is complete.

Expand the Encoding type drop-down menu, then select Unicode (UTF-8).

Select UPLOAD.

⚠️Under Data mapping, you must map these two fields only:

You must not map any other fields. Set any other fields on the Data mapping page to Skip column.⚠️
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Select FINISH.

Create a new segment called Potential duplicates.

To learn more about creating a segment, check out the article Create a segment.

Drag the data field block onto your segment Include area. Then select the block to open the rule settings.

Select the data field POTENTIAL_DUPLICATE.
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Expand the rule drop-down menu, select Is yes, then select OK.

Drag the data field block onto your segment Exclude area. Then select the block to open the rule settings.

Select the data field Email.

Expand the rule drop-down menu, select Is not empty, then select OK.
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Select SAVE, then GENERATE SEGMENT.

Go to Audience > Segments.

Select the Potential duplicates checkbox.
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Expand the MORE ACTIONS drop-down menu and select Convert to list.

Go to Audience > Lists, select the checkbox for the Potential duplicates list, then expand the MORE ACTIONS drop-down menu, then select Remove selected contacts from your account.
⚠️This action deletes contacts with just a mobile number and permanently erases their engagement data. If you're unsure, contact your Customer Success Manager or our Support team for help.
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Confirm you understand the conditions, then select DELETE CONTACTS.

Periodically refresh the Lists page until the contact count for the Potential duplicates list reaches zero.

Expand the User menu, then go to Settings > General > Recycle bin.

Expand the MORE ACTIONS drop-down menu, then select Empty recycle bin.

Go to Audience > Contacts, then expand the NEW CONTACT drop-down menu and select Import contacts.

For File, select CHOOSE FILE and select the same CSV file that you edited and uploaded previously.
Optionally, for Email address to notify, enter an email address to receive a notification when the import is complete.

Expand the Encoding type drop-down menu, then select Unicode (UTF-8).

Select UPLOAD.

Under Data mapping, map the following fields:

For Potential_duplicate, expand the drop-down menu and select Skip column.
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Select FINISH to merge your contact data.