When we used QB Desktop, we used to use a 3rd party portal called GoToMyAccounts GoToMyAccounts – branded self-service customer portal for QuickBooks

It's a really slick system and Mark, the owner and lead dev, is really responsive on support. The email delivery mechanism on this is WAAAAY better than QBO, allowing you to hand off to your own mail servers if you prefer, do proper branding and personalisation with a fully customisable template and has proper message delivery diags. 

We are going to go back to it for message delivery and cross-charge Quickbooks for the missing fundamental features in their own system. 

If they had any sense, they would buy this platform and integrate it!!!