How to turn from your Exim into a mandrill with the provision of api?

Question

PHP

Hello.
Well, the question is not very correct.
The bottom line is that I can send letters from my exim (mail server) to inbox only from my email addresses.
How to make it possible to send from different postal addresses? What would not be spam?
Because when I send from my domain and I put another address from where I send it, it goes to spam!
PS I'm not a spammer. I fight them myself. It's just not the first time I've run into this problem. For your mailing needs.
Again, not for spam.