Yes, bidders have an option to submit their bid by replying to the bid invitation email sent from Procore with an attachment. See Submit a Bid. This is meant to serve as an alternative to bidders emailing a bid completely outside of Procore, where you would need to manually enter their bid on their behalf.
If a bid is submitted by replying to the bid invitation email, the following information is automatically updated in the Bidding tool:
Note that you will need to review any submitted files in the 'Attachments' section of the bidder's response page. See Review Submitted Bids.