In case you are to diagnose if you sent the particular invoice to the specific customer, stop worrying about the memory. The criteria you used depends upon the need for viewing the history for solo invoices or you are looking to go if you emailed more than one invoices.
Sending the Single File
Original Source: https://quickbookshelplineuk.sitey.me/blog/identify-the-method-to-send-the-emails-in-the-quickbooks-software
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