(09-04-2018, 08:51 AM)ORiOn Wrote: I think my main problem is with rDNS, I get this error on mail-tester.com
And on ssl-tools.net:
I have no idea what to do...
There are lots of reasons why emails you send would be seen as spam, but I agree with wormsunited above, you must have reverse DNS (PTR records) set up for your sending IP address, and the PTR record must match the hostname your server gives out upon SMTP connection (the HELO) otherwise a lot of receiving email providers will see any mail you send out, see a dynamic-looking IP address and not even attempt to deliver it.
You should also get SSL/TLS sorted out as you stand a better chance of the receiving server accepting you mails if your own sending server sends the mails securely.
There's loads of info online about how to configure Postfix for using secure ports etc., and installing certificates from the likes of Let's Encrypt, but if you're coming from having "no idea what to do" then you'll need to be up for a challenge to get through it...
Keith