Bitrix24 20.0.0 CRM Source
Bitrix24 is a comprehensive free CRM system available both online and as self hosted software that can be installed on your own server. If you go for this option, you’ll get access to open source code as well. Cloud version of Bitrix24 doesn’t have any limits, other than 12 users and 5 GB worth of online storage - you get unlimited leads, contacts, companies, deals, products, quotes, invoices and email marketing. Bitrix24 is also the only free CRM system that comes with integrated call center, so you can make and receive phone calls to/from your CRM as soon are you register.