Microsoft Outlook is a web-based suite of webmail, contacts, tasks, and calendaring services.
Store the original email beside each named attachment.
Your marked client or case emails go into the shared archive beside their attachments, with a folder link for the filing owner.
Place flagged project attachments in the right folder and flag conflicts.
Your flagged email attachments go to the archive folders you set up, with original filenames and a report of files needing attention.