I have created an email folder "Ebay and Paypal".

I move all the emails from them to this folder. It does not clog up my in box and every six months I do a purge of the special folder. I keep my Postage receipts with the DC attached to the details page that I print from Paypal and file it by month. I feel like I should have all I need if a question is asked. What the customer bought, when it shipped, DC number, Ebay item number, etc.