PHPMailer over SMTP - gets into SPAM, what's wrong?

Question

PHP

I use PHPMailer, the letter is sent via POP3 protocol, via SMTP - goes to SPAM, what's wrong?
using PHPMailer from github

Answer 1

https://www.mail-tester.com/

Answer 2

DKIM, DMARC, SPF set up!

Answer 3

Google: SPF, DKIM, domain and address verification.

Answer 4

Are you sending via smtp to the Yandex server or directly?
Are you trying to forge addresses (in SMTP FROM, in the From header)?

Answer 5

We receive letters via pop3, but do not send them
. If the message is sent via SMTP, you need to take into account several points.
1. Is authorization configured when sending a letter? If yes, add the IP address of the server from which the PHP mailer is running to the SPF entry. If not, step 2.
2. On your mail server, let's relay messages from your web server's ip address and add the web server's IP address record to the SPF. Yes, you will not be able to set up a DKIM signature - but for basic work, this setting is enough.