Spam emails when registering, how to avoid this?

Question

Mail server

Greetings,

The problem is this:

About 5000 people register on the site every day - letters with an activation code end up in spam or do not reach at all (mail list rambler)

They end up in spam if sent using the mail function
There are very small limits on ppd.yandex if sent via smtp.

Is it an option to only buy/connect an external smtp, especially to ensure delivery to mail/rambler?

Answer 1

set up mail correctly.
habrahabr.ru/company/mailru/blog/239963

Answer 2

DKIM certificate.

Answer 3

I registered DKIM for the domain - I took those that Amazon SES gives and all the same in spam. Perhaps you need to change the email address?

Answer 4

set up your mail server correctly