I send an email using a script, but the letters fall into spam, how can I fix it?

Question

Email

The script is in a subdomain.
For example, mail writes E
We cannot verify the identity of the sender. We recommend that you be more careful when performing the actions indicated in the letter. More

Answer 1

Configure for DMARC, DKIM, SPF domain.
Where the script is located is not important, the settings of the mail server through which you send the letter are important.
So that in the DNS of the mailer domain it is allowed to send messages on behalf of the domain specified by the sender.
You can check it here: https://www.mail-tester.com/
You send a letter to the specified address and see what's wrong.
And another service for checking records in DNS: https://mxtoolbox.com/