Multiple email messages can be forwarded as a collection in a single message. This is a more efficient way to forward multiple messages rather than clicking Forward for each message.
For example, if you have five messages about a project and you want to forward all of the messages to someone on your team, you can forward all five messages as attachments in a single message. The recipient can click on the attachment to view the message in the Reading Pane or double-click each attachment to open it in a message window.
In Mail, click one of the messages, press and hold CTRL, and then click each additional message.
On the Home tab, in the Respond group, click Forward.
Note: Multiple messages must be selected in step 1 if you want the Forward command to attach messages as attachments. If you want to forward a single message as an attachment, in the Respond group, click More, and then click Forward as Attachment.
All messages selected in step 1 are added as an attachment in a new message.