When i send out invoices and estimates does the online version save the email address that I frequently send them out too

Hey there, @LPSCONTRACTINGCORP.  

Yes, the QuickBooks Online version will remember the customer emails that you use or enter when sending the invoices. When you click the To Cc/Bcc field, the email addresses that you recently used will appear as entries. All need to do is select which email you want to use again and send the transaction. 

You can review the screenshot below as your reference. 

Moreover, you can customize the appearance and layout of your sales forms in QuickBooks. Doing this lets you decide what your customers see and add the info that matters the most to your business. 

If you have additional questions about sending invoices in QuickBooks Online, just post them again to the thread. I'll be glad to help you further.

Thank you