I am creating own mail server. I am using Haraka (http://haraka.github.io/). But I am little confused about the relay thing. How to make relay my mail server so that I can send mail using other domain(DKIM and SPF verified).
I want mail in receiver inbox not in Spam. Right now mail is received in spam. What is relay in particular ? Can anyone help ?
What I've got is that you're having a problem with sending mail on behalf of "other domain".
Given that "other domain" mail reaches its destination (even in SPAM folder) I assume that you've configured your relay right.
Key thing to notice is that DKIM and SPF records not only need to be validated but also need to be aligned with your "other domain". It's a common scenario when SPF/DKIM validations 'pass' but overall DMARC policy 'fails'.
Providing both your message headers (to check how it was processed) and your other domain name (to check how SPF/DKIM/DMARC records configured) would help a lot.