Vps mail configuration

I have a reseller account in shared hosting and a vps. both are in different server. but when i send mail from shared hosting it goes to inbox and from vps it goes to spam with same content and same domain. The issue is in vps mail configuration. So i want two solutions either or. 1. i want my smtp(outgoing) from old reseller server, and pop3(incoming) in new vps for total server as i have multiple hosting in the new vps. 2. else i have to buy a new vps and send you total details. you have to setup the total server with all securities and configuration. and send some mail from it so i can check it goes to inbox.