We're quite happy with what Linagora [1] offered a few years back. It's a French company so they work within EU framework of law. Their products are all open so

We're quite happy with what Linagora [1] offered a few years back. It's a French company so they work within EU framework of law. Their products are all open source, they only sell support services. [1] : https://www.linagora.com/en/ https://www.linagora.com/en/