Gmail for Business

I am currently not teaching, but want to maintain my license in case I choose to return to the profession in the future.  I now own a business called Chilled which offers customers prepackaged freezer meals and mason jar salads among other products.  I am constantly in contact with my customers via email - in fact it is one of the only ways I communicate with some of them.  Because I receive so many emails, I have to be able to organize them efficiently.  I have always been one that once an email is "done" it gets deleted.  However that has not been working well for me lately as I need information from past customers in order to operate effectively.  Today I needed to deliver to a house I had been to previously but didn't have the address since I deleted the email.  If I would have used labels in gmail for that customer, I could have easily found them.  My plan is to create labels for emails with identifying information for each city so I can easily sort through them and get their addresses or other info I need.