For your information , I am aware of these back up clients and the cloud they can sync to :
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SyncBackPro
http://www.2brightsparks.com/syncback/sbpro.html
Google Drive, Office 365 (OneDrive for Business and SharePoint), OneDrive, Box, Dropbox, SugarSync , Amazon Glacier S3 , Amazon Cloud , Google Storage and Microsoft Azure support

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Arq for Windows and Arq for Mac
https://www.arqbackup.com/pricing/
Amazon Cloud Drive, Amazon Web Services, Dropbox, Google Drive, Google Cloud Storage, or OneDrive account

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Syncovery
https://www.syncovery.com/matrix/ --- features comparison
Supports various Internet protocols, including FTP, FTPS, SFTP/SSH, WebDAV, SSL, HTTP, as well as these cloud services: Amazon S3 and compatible services, Microsoft Azure, Rackspace Cloud Files, Microsoft OneDrive (formerly SkyDrive), Google Drive and Google Docs, DropBox, Box.com, and more....Sugarsync

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Duplicati
www.duplicati.com/
https://en.wikipedia.org/wiki/Duplicati
Duplicati supports not only various online backup services like OneDrive,[1] Amazon S3, Rackspace Cloud Files, Tahoe LAFS, Google Docs but also any servers that support SSH/SFTP, WebDAV, or FTP.
Duplicati is a backup client that securely stores encrypted, incremental, compressed backups on cloud storage services and remote file servers. It works with Amazon S3, Windows Live SkyDrive, Google Drive (Google Docs), Rackspace Cloud Files or WebDAV, SSH, FTP (and many more). Duplicati is open source and free.

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BitTorrent Sync
https://getsync.com/
Sync easily moves anything, anywhere - all the benefits of the cloud, none of the limitations. Available for Windows, Mac, Linux, iOS, and Android.

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Strongsync
https://secure.expandrive.com/store
https://www.expandrive.com/apps/strongysnc/
Control your data. Strongsync lets you connect to your own SFTP server or Amazon S3 account so you stay in complete control of your data.
Strongsync is a Mac/Windows app providing Dropbox-like sync and backup to DreamObjects......

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ExpanDrive
http://www.expandrive.com/apps/expandrive/
ExpanDrive creates a virtual USB drive that connects to all major cloud storage providers such as Dropbox, Google Drive, Box, OneDrive, Openstack Swift, Amazon S3 or your own SFTP, FTP or WebDAV server.

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CloudBerry
http://www.cloudberrylab.com/calc.aspx
Online cloud backup and storage management solutions powered by Amazon S3, Glacier, Microsoft Azure, Google Cloud and designed for SMBs and MSPs.
--- Avoid Cloud Vendor Lock-In
With Cloudberry you are free to choose optimal storage for your backups. Don't be locked in with a backup service and paying 2x times more for the backup storage. With over 20 supported cloud storage destinations, CloudBerry Backup give you freedom of choice, ensuring data accessibility and portability.
Featured Cloud Providers
Amazon S3
Amazon Glacier
Microsoft Azure
Google Cloud Storage
Rackspace Cloud Files
OpenStack
HP Cloud
IBM SoftLayer
Google Drive
Other Cloud Providers
Google Nearline Storage
Eucalyptus
Clodo
Scality
Cloudian
DreamObjects Cloud Storage
Aruba Cloud
Hitachi Content Platform
ThinkOn
IDC Frontier
LeoNovus
CloudWatt
HavenCo
Tiscali
SFR
Lunacloud
CenturyLink
Enter Cloud Suite
QNAP
Google Drive
HP Helion

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CloudBacko
http://www.cloudbacko.com/en/cloudbacko-advanced-cloud-local...
"Backup all servers, databases, virtual machines & workstations
Need a cloud / online / offsite / remote / local backup solution for backing up Microsoft Exchange Server (EDB and mail level backups), Microsoft SQL Server, VMware vSphere ESXi (both Paid and Free versions), Hyper-V, Lotus Domino, Lotus Notes, Oracle Database, MySQL, Windows System, Windows System State, as well as Files in desktops and laptops? CloudBacko supports them all."

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Filement provides you with secure and direct access to your ...
http://www.filement.com/users/use-cases
Filement provides users with the ability to manage all their devices (PCs, Macs and Linux, Smartphones, Tablets, Smart Routers), cloud and remote services (Google Drive, Dropbox, OneDrive, Rackspace, FTP ect.).

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GoodSync: File Sync & Backup Software
http://www.goodsync.com/features
Backup and sync your files with ease using GoodSync. Our simple and secure software will ensure that you never lose your files. Download GoodSync Free ...
--- Supports:
Cloud Server Folders
Amazon S3
Dropbox
FTP
Google Drive (Docs)
OneDrive by MS
OneDrive Pro (Sharepoint) by MS
Office365 by MS
SkyDrive by MS
SFTP (SSH)
WebDAV
Windows Azure by MS
(Source: https://discussion.dreamhost.com/thread-145071.html
January 2015
3rd party backup software options)

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Boxcryptor
https://www.boxcryptor.com/en/pricing
With Boxcryptor you can encrypt your files on Dropbox, Google Drive, Microsoft OneDrive, SugarSync, Box and many other storage providers.
It also supports all the clouds that use the WebDAV standard such as Cubby, Strato HiDrive, and ownCloud.