QB Issue Resolution:

You List them in one line in the email field, and another long list is available in the cc field. Those two fields are part of Send Forms. Each allows for 1,023 characters.

You separate with Semi-colons and then a space.

Here:

https://www.accountexnetwork.com/blog/2014/07/email-quickbooks-invoices-multiple-recipients/

Resolution for Issue 'I want to send estimates and emails to 4 people at one time. How can I keep their emails in permantly so they can be sent to all 4 people each time.' available: Yes (Solved).
Source: Intuit Community forum.

I want to send estimates and emails to 4 people at one time. How can I keep their emails in permantly so they can be sent to all 4 people each time.: this issue or error code is a known issue in Quickbooks Online (QBO) and/or Quickbooks. Support for this issue is available either by self-service or paid support options. Experts are available to resolve your Quickbooks issue to ensure minimal downtime and continue running your business. First try to resolve the issue yourself by looking for a resolution described below. If it is a complex issue or you are unable to solve the issue, you may contact us by clicking here or by using other support options.

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