Why not? It's an IMAP service, you could use it with the client you prefer. Obvius GMAIL far way better for mail classification (promotional, transactional, spam). But I doubt any other service can do better than GMAIL with features.

gmail webmail client and spam/classification filters are already something above by far any other competitor. This is the added value I would like to see in a mailbox, not just another IMAP service.