Hello,
Let me give the best things to make the emails to land into email inbox.
1. SPF record - Authenticated IP address which are authorized to send emails.
2. DKIM - Incase, if you use postfix/sendmail, setup a opendkim and allow the domain to sign all the outgoiing emails from the server.
3. Reverse DNS, Forward DNS- Make sure there exist a forward/reverse DNS to the domain name to IP address.
4. Throttling email based on recipient - You may have to setup a throttle email based on recipient for major email providers like gmail,. hotmail, aol, yahoo. You can refer our blog incase if you would like to explore on yourself.
blog[dot]pheonixsolutions[dot]com/configure-thrttling-for-outgoing-mails-in-postfix/
As of now, we don't have any rating to show you up. However, if you want us to try on this project then please do ping us.
Thanks.