Continuing to the past topic:
File Manager .
1) The interface was created to work on a tablet computer.
2) Not gmail, because you need to store messages on your servers, you need to work with any domains, including your own.
3) One of the advantages of a client created in PHP is its accessibility from any place where there is Internet.
4) Not roundcube, since this email client uses the PHPMailer library, so it can work with POP3, IMAP mailboxes and send mail via the SMTP protocol.
5) The mail client, as well as the
File Manager, has been removed from another project.

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DemoLogin and Password: mailer / mailer
githubengineRequirements
PHP> 5.2
PDO Database: MySQL, PostgreSQL, SQLite (mysql tested)
JSON PHP support
Required write permissions to directories: / attaches / upload
Database dump: /sql/mail.sql
Login and Password: mailer / mailer
GPL

The application is still quite raw, requires improvements in terms of interface, usability and correcting possible errors. The purpose of the topic: to find interested people and listen to tips for improvement.
PS Imperceptible bonuses:
1) you can view mail from the keyboard using the arrows:
right to view message
left - return to the list of messages
up, down - select a message from the list
2) from the tablet, you can just scroll through the list of messages (for some reason, the DIV scrolls on DIV on Android, I did it without it)