Forward a message or attachment on Mac
You can forward a message (or an attachment such as a photo or video) from a conversation.
In the Messages app on your Mac, select a conversation.
Control-click the message or attachment, then choose Forward.
Add a recipient, then press Return.
The message or attachment is sent.
Note: If you’re restricted to sending and receiving messages with only certain people, an hourglass icon appears next to those people you can’t forward a message to.