Hello there, @ticelles. 

In QuickBooks Online (QBO), you can enter multiple emails in your customer's profile, invoices, or estimates. Let me walk you through the process of adding the email addresses to the customer's profile.

Before we begin, here are some things you should know about sending an email to multiple email addresses:

• There is a 100-character limit in the recipient's email address field. (Note: This limit includes spaces.)
• The system will not allow you to send an email to the same address more than once. (Note: If the email address is added twice, the other email addresses listed after the duplicate email address will not receive the email.)
• Cc recipients are visible to all other recipients.
• Bcc recipients are not visible to anyone.

Aside from that, you can send an email to multiple addresses by performing the following:

• Typing in multiple email addresses separated by a comma and a space.
• Using the Cc (carbon copy) or Bcc (blind carbon copy) fields.

Please check out the sample snips attached below on how add them on your customers profile and on sales forms:

This article will show you how to add multiple email addresses to reports and sales entries: Email a sales form or report to multiple email addresses.

You can use our self-help articles to help you manage your company's income,payments, and other sales-related activities.

Know that my doors are always open to help if there's anything else you need with sales transactions or with QuickBooks. Thanks for coming, and have a good one!