Local Mail server send/rcvd mail trhough Mikrotik router

RouterOS Forwarding Protocols
1

Problem:
I have a mail server (172.16.0.10) in my LAN. Its only have on LAN card. Mikrotik manage my LAN PCs Internet. Now I want to configure Mikrotik as mail send/rcvd firewall media (currently clearOS manage this mail server). mail server entry have on godaddy server. mail server entry is mail.btibd.org (115.127.34.90). 115.127.34.90 is also configured my Mikrotik WAN port. — please give step by step solution for this issue.

2

Check this: https://wiki.mikrotik.com/wiki/Manual:IP/Firewall/NAT , section “Destination NAT”