Hi @treasurer36,
As of the moment, there isn't an option to customize the email domain in QuickBooks Online (QBO).
The quickbooks@notification.intuit.com email is the default address in QBO when sending transactions and reports.
But you can manually send your transactions or reports to your customer and vendors. This way, you can personally customize your email address.
Just download the PDF file of your transactions or reports and include it as an attachment when sending your emails.
Lastly, you can also read this article which can be your guide for any future tasks: Make Sure you Receive Important Email Messages from Intuit.
As always, you leave a comment below or start a new thread if you have any other concerns. I'll be happy to help.
