Assuming that you have access to a developer (or are one yourself), you could extend the Customer table and customize the OnAfterValidate trigger to insert a Document Layout (Custom Report Selection record) immediately after the Email field loses focus.
For generating the Document Layouts for your existing Customers, a simple processing Codeunit could be written to iterate through your Customers, and for each, insert a Custom Report Selection record for the appropriate Document Layout and current Customer Email. You could then run it once on the Job Queue to generate all of your Document Layouts.
The data you would need to fill in would be:
Source Type: 18 (Customer)
Source No.: (Customer No.)
Usage: S.Invoice (based on screenshot)
Sequence: (Likely 1)
Report ID: 69006 (based on screenshot)
Send To Email: (Customer.Email)
Then, also potentially Use for Email Attachment or Use for Email Body.
It is effectively the same process for both tasks--inserting a Document Layout (Custom Report Selection) based on a selected Customer.
Hope that helps.
Benito
