Hello, im facing the issue that one or more freemail providers mark emails sent from my server (my own domain) as a spam and placing them into spam folder. So custommers do not receive my emails. Please what exactly i need to setup in cPanel WHM, is there any guide please? Any example please what to do and check to gain trust?
The best way is if they are your customers, get them to whitelist emails originating from your domain. Normally you would get into the spam folder if you send out a large number of unsolicited mail. Also check that your MX records, rDNS, DomainKeys, etc are all set up correctly. You may want to ask your hosting provider for assistance on this.
Authenticate all outgoing emails (SMTP secure port 465 - SSL), setup proper DomainKeys and SPF records on cPanel (Email Authentication icon), check MX record, if possible - use static/dynamic IP and make sure reverse DNS is properly setup. Once done, send an outgoing mail to freemail provider. Check if it still spam. Examine headers to make sure you get where are your mails are getting wrong. Check also your server's mail log, incase there was something there.
Check for SPF and DomainKeys records. Check if reverse DNS is setup. Check if the IP is on any blacklists.