- Mail box from which will be sending e-mails from the site, registered in the control panel hosting ISPmanager.
For this purpose, in the WWW domain properties in the administrator email field specify the existing mail address created on the server.
The site will now be able to successfully send emails through the php mail functionality (using sendmail) on behalf of that box.
- In order for emails sent by the sites scripts to reach all mailboxes and not get into spam, you need to send such emails with the sender of any mailbox created on the same domain, not mailboxes on gmail, ya.ru, mail.ru, etc.
Also in the settings of your script (site control panel - CMS) leave the default data, preferably prescribing as e-mail sender system letters created on the server's existing mail address.