Customer attachment in Dynamics 365 Finance and Operations refers to the process of linking a specific customer record to a transaction or set of transactions within the system. This allows businesses to easily track the history of customer interactions and transactions, as well as view customer-specific information such as credit limits, payment terms, and purchase history.
By using customer attachment, businesses can improve their customer service and build stronger relationships with their customers. For example, if a customer calls to inquire about an order, a customer service representative can quickly access the customer’s record and view all past transactions and interactions to provide more personalized and effective assistance.
How to export customer attachments
Go to Data management workspace > Click on export tile.
Create new, provide the group name and description.
Add Customer V2 attachments entity
Click on Export now.
Click on Download package to download the file. 
Once the file is download, extract the file. The extracted file looks like below.
You will have Resources folder and under Resources folder, you will have another folder name with the entity and all files inside the folder.
Note: We must use this package as reference and import back to Dynamics 365 F&O. 
How to import customer attachments
Edit the Customer V2 attachments excel and delete the existing data.
FileContentsFileName(Mandatory) – This should be your filename.extension.
For example, if you are importing document file then it must be TestFile.docx
The physical file TestFile.docx must be inside folder.
Resources/Customer V2 attachments/TestFile.docx
Your folder should be like this.
Now, select files in the main folder and make it zip file.
Go to Data management workspace > Click on import tile
Create new, provide the group name and description.
Add the package.
Click on import now. It should show succeeded status.
Now, validate the document in the customer record.
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