Sync2 is described as 'Synchronize Microsoft Outlook between computers using external USB device, shared network folder or FTP. Sync Outlook contacts, calendars (appointments, meetings and all events), tasks, notes and e-mails without a server. Share Outlook folders on your laptop with your desktop' and is an app in the Office & Productivity category. There are more than 10 alternatives to Sync2 for a variety of platforms, including Windows, Online / Web-based, Android, iPhone and Mac. The best alternative is iCloud, which is free. Other great apps like Sync2 are EteSync (Paid, Open Source), AkrutoSync (Paid), PhoneCopy (Freemium) and Outlook CalDav Synchronizer (Free, Open Source).
PhoneCopy is the easiest way to backup, manage, and synchronize personal data from a mobile phone to the cloud. Phonecopy securely manages phonebook contacts, calendar events, SMS messages, photos, and videos. All data are accessible via a web browser.
Free Outlook Plugin, which synchronizes events, tasks and contacts between Outlook and Google, SOGo, Horde or any other CalDAV or CardDAV server. Supported Outlook versions are 2016, 2013, 2010 and 2007.
GO Contact Sync Mod is an open source tool to synchronize your Microsoft Outlook contacts with Google Mail. With this tool you do not need to enter your contact details more than once, always have the latest version everywhere: in Outlook and in Google.
SyncMate syncs data on Mac with Android and iOS devices, Windows services (Outlook, Office 365 Business and Office 365 Home accounts), other Macs, Google, Dropbox and iCloud accounts, any mounted storage devices, MTP devices.