You can only send a new message to project teams for tenders you are involved in. Go to the related Opportunity Page from My Proposals and Quotes, click on Messages, and then click New Message to raise a clarification question with the buying organisation.

To attach a document or file to your message:
While drafting your new message, click the paperclip icon (or Add Attachment button) within the message window. Select the file from your computer and ensure it finishes uploading before you click send.

Note: The maximum file size limit is 10MB, and you can only attach one file per message. If you have multiple files, you will need to combine them into a single ZIP folder before attaching.

Alternatively, you can view and reply to messages received for all tenders from the Message Center section on the home page of the portal once logged in. 

Please see the Message Center help article for more information.