SuiteCRM
The multi-award winning SuiteCRM is the world's best open source CRM.
...The open source format of SuiteCRM means that users can scale the application & customize it’s many modules and features to meet their specific business needs. SuiteCRM suits any business size, requirement, or industry. It can be hosted on-premise, as a Software as a Service solution or in a business’s own private cloud, allowing businesses to maintain GDPR compliance, whilst remaining in full control of their own data.
SuiteCRM provides users with actionable insights into customer behaviour, leads, accounts, and more. Making it easy for Sales, Marketing and Customer Service departments to discover key information that will help a business to grow, retain, and delight their customers.