Email goes to spam in Gmail and other email providers

I am having a problem lately to send email from cpanel to gmail email where the email I send goes to spam gmail, even though I have used ssl, set up spf & dkim which usually functions to avoid spam and ptr records on the provider we use I checked on several sites, the list of black IPs and my IP was not blacklisted but still, emails sent from my webmail go to the spam list, so they have to be whitelisted if I want my e-mail messages not to be spam, the problem is not everything I send e-mails is someone I know and that is very troublesome because there are no notifications message goes to the person I sent the e-mail can anyone help my problem?