I do not have an SMTP server and frankly do not want the attention of "25/tcp open smtp" according to nmap scans!

I have tried blocking it using:

/ip firewall filter add chain=forward protocol=tcp dst-port=25 insert-before=0 action=drop


and that didn't work. So I tried forwarding port 25 to a non-existent ip address and that did not work. Port 25 should show as being closed according to port scanning. Why is it showing as open and how to get it to show as closed?

Please post "/ip firewall filter". You should be blocking more than smtp. You should have as a minimum the protection in the "router protection" in this wiki:
http://wiki.mikrotik.com/wiki/Manual:IP/Firewall/Filter