Research and evaluate products available on AppExchange to send mass emails is the action that the app builder should take to meet the requirement of broadcasting an email to 7,000 contacts in Salesforce on a regular basis. AppExchange is a marketplace where app builders can find products or solutions that can extend Salesforce functionality. There are many products on AppExchange that can send mass emails without hitting the Salesforce limit. Request Salesforce increase the number of maximum daily emails, develop Apex code and Lightning web component to send daily emails, and export Contacts to a CSV file and use an email client to send the emails are not valid or recommended actions.

As of the Winter '24 release, Salesforce introduced the ability to send outbound messages directly from Flow. This makes Flow the best choice for automating the notification to an external system when a lift is sold, fulfilling the need for both checking the custom To Be Installed checkbox and sending the notification the next day.
Flow: With this new functionality, Flow is now the most versatile automation tool for this use case. You can:
Create a scheduled path that triggers the next day after the lift is sold (e.g., when a record meets the criteria such as the checkbox being checked).
Send the outbound message to notify the external system about the lift installation.
Perform all of this declaratively, replacing the need for Workflow, which previously was the go-to for outbound messages.
Why not Workflow anymore? Although Workflow still supports outbound messages, Flow is the preferred tool now, as Salesforce is deprecating Workflow rules and Process Builder in favor of Flow. Flow also allows for more complex logic and actions, providing flexibility in future-proofing automation.
Reference:
Winter '24 Flow Outbound Message