I have configured the email server a few days ago. I noticed one thing that if I send mail to Gmail, it is delivering to my email inbox properly. Even if I send mail to another service provider's hosting or email server, it is delivering to my inbox properly. But when I send email in Outlook/Yahoo/Hotmail, my email is repeatedly going to the spam folder. After checking the email header, I saw that Outlook is failing my DKIM authentication which other mail services show as passing. I have checked their email server with some of my friends and they are also having the same problem as me. I have configured a new server but even after that I am still having the problem. Many of my friends are having the same problem. Now how can I fix this? I have a proper guideline. I am very worried about this.