IvanAllhiser
Please read the requirements before installing. 1.16.x requires PHP 8.0. Downgrade your PHP to 8.0, install all the extensions listed in admin panel > information tab, and make sure php-imap extension is installed. You may also want to ensure you have the appropriate OpenSSL version installed on your server. You may also want to test imap connection from the server to ensure itโs possible.
If you are getting TCP disconnect it might be a firewall issue, or something of the sorts. Contact your server/network admin to ensure the port is open on the server and nothing is blocking the connection.
If all else fails you can contact your mail provider.
Cheers.