The Mail application can work with any mailboxes. The application is integrated with all processes and contacts of the system, when a new letter is received, a contact is created and placed in the contacts database, when a letter is opened, the letter is marked as read. The entire history of correspondence is available in the system throughout the entire period of using the system. If necessary, you can send files (invoices, documents, etc.) from the system to clients/contacts. The application was created for the convenience of working in a system with various entities, and this is not necessarily a document.