Availability of “Select all” when using Mail

When using Mail, I would like to use the “Select All” option when editing text. I would like to copy all of the text to transfer the text to the “Pages” App for easier editing. If I’m using the “Sent” option to look at my previously sent mail messages, the “Select All” option is available. However if I’m using the “Drafts” option, the “Select All” option is not provided. This means I have to manually select the text. Is there some way to copy all of the text? Thank you.