Microsoft has released instructions on how to connect Office 365 (the service behind SUmail) using different email clients for Windows and the Mac. ITS recommends that you use IMAP to configure your email client if Exchange ActiveSync is not available:
IMPORTANT:
Use your netid@syr.edu address for your email address and Username.
You can access the Outlook Web App for SUmail at: https://sumail.syr.edu
NOTE: You need to sign into your account using the Outlook Web App at least once before you can configure other email clients to access your SUmail account.