Preferences: Online Sync tab
From the 
Options button on the main toolbar, select 
Account & Email (or from the Edit menu, select Preferences, then the Online Sync tab).
My Account Credentials: The email address and password on your Main Street account online, need to match what is stored in your Boulevard program to ensure you continue to receive current product updates, install available software releases, and sync to the Avenue app. See Updating Your Email Address & Password for more information.
Outgoing Email Settings: Choose whether to link your email address inside Boulevard or launch a Desktop client such as Outlook, Windows Mail, Thunderbird, etc.
Avenue Mobile Sync: This section only applies if you have a current subscription to the Avenue app. Choose which information and how much is transferred to the app when a sync is performed. Also, an additional option to be prompted to sync to the Avenue app when exiting Boulevard.