Currently there isn't an option to directly attach a Teams file to email via Teams.
Here is a link from the Teams uservoice forum asking for this feature: Add "attach to email" option from Files in Teams
Please consider upvoting it or leaving a comment to submit your feedback on this feature.
Thanks for your understanding.
If the answer is helpful, please click "Accept Answer" and kindly upvote it. If you have extra questions about this answer, please click "Comment".
Note: Please follow the steps in our documentation to enable e-mail notifications if you want to receive the related email notification for this thread.