Quickbooks apps or integrations that allow for custom invoice emails?

If you're trying to do anything other than send a basic institutional looking Invoice, Statement, etc., don't try to do it with QB's email.

Just print the Invoice, etc. as PDF and use your company email.  You'll spend too much time trying to make the QB's email to do something it was never designed to do.

Do you know if there are integrations or apps that will allow me to batch download the invoices, and batch send through my company email? 

Glad to have you here in the Community page, kashdesign. 

Allow me to fill you in on everything you need about downloading the invoices and sending email by batch in QuickBooks Online.

The option to download invoices and sending invoices by batch is unavailable in QuickBooks Online.  As a workaround, I recommend integrating your QBO company with a third-party application that will allow you to do such. 

Though, we're unable to provide recommendations on which one to use. I suggest you visit the Intuit Marketplace to check for available apps that you can take advantage of.

Here are some articles that you can check anytime for additional reference about handling sales forms in QBO:

• Learn how to personalize and add specific info to sales forms.
• Email and customize sales form.

You already know where to find me in case you need more help with managing invoices. Just comment down below. I'm here to help always. Have a good day!

@kashdesign 

What kind of business do you run? An interior designer? You may need an invoicing app or a specific app for your industry with invoicing features to integrate with QBO.