Setting up a remote mail server

Question

postfix

Given:
site server example.com
mail server mail.example.com It is

required to configure sending emails via mail.example.com so that emails pass all spam checks

Actually sending emails is configured, but emails end up in spam, I sin on the absence of DKIM-Signature in the headers emails

Question: How do I set up DKIM-Signature email signing?

I followed this tutorial: help.ubuntu.com/community/Postfix/DKIM

but the letters still come without a signature, whoever came across throw links to tutorials, I have already killed a day for this activity (

Answer 1

“letters end up in spam” - which recipients? Do they (recipients) have any diagnostics about spam written in their email headers? DKIM won't help if your server's IP is in RBL, or if the text is spam (according to some spamassassin).

Answer 2

PTR for mail server IP registered?