Send read receipts in Messages on Mac
You can send read receipts so that people you have a conversation with know when you’ve read their messages.
You can send read receipts for all conversations you have using an account, or for just one conversation. If you turn on read receipts for an account, you can still turn them off for a single conversation—and vice versa.
Send read receipts for one conversation
In the Messages app on your Mac, select a conversation, then click Details in the top-right corner.
Select Send Read Receipts.
Send read receipts for all conversations
In the Messages app on your Mac, choose Messages > Preferences, then click iMessage.
In the Settings pane, select “Send read receipts.”