You can't attach a folder. You either attach each message separately, or zip the folder and its contents into a single file and attach that. You can probably use ctrl+a to select all the messages in the folder and attach them en masse. Zipping has the obvious benefit of (usually) reducing the size of the email payload, but has the downside of confusing some less techie people.

A folder isn't a real thing; it is just a list of the names of other things.

Oh, you could forward them by creating a new message, then adding the messages from the folder by selecting and then drag-and-drop onto your new message's address box.

Another option is to select the messages, then right-click, Forward As Attachments, to open a new message with all the selected messages added as eml attachments.

Thank you for your suggestions. I'm going to give them a try now to see if I can work it out.

sfhowes, thank you for your helpful response. I just did what you suggested and it worked perfectly. Many thanks. Hope you have a great day. Thank you Zenos too, for taking the time to respond!