Cisco Firewall :: 6552 Static Entries With Same Ip Address But Different Ports

Our proxy/anti-smap/IPS box called PROXY is behind our Cisco ASA firewall. The PROXY is set in transparent mode.The PROXY internal ip is 1.1.1.1 (internal ip)We have the MX record for mail.domain.com with public ip 9.2.7.5 (public ip as we entered with ISP public DNS)What happens now is that the emails that come through get "caught" by the PROXY and then we setup a thing whereby the emails are then forwarded from PROXY to our mail.domain.com server. Also, we made a static entry in PROXY whereby we can https to our email server for the outlook web access from outside of work therefore allowing for users to see the outlook web access web page.On the Cisco firewall, we put the static entry that 9.2.7.5 is mapped to 1.1.1.1 thus the mail server public ip is mapped to the PROXY.
 
Now, the box has this thing whereby it sends an email to all staff once a day telling them how many mails are legit, how many rejected and how many are spam - the spam emails are listed within the email and staff can at a click of a release button next to each spam email release a particular email from the PROXY box and make it to into their inbox.  This works fine from the inside network, but I have issues from the outside due to the DNS and other things.I also put in the PROXY that any network can release spam and that our staff vlan can release emails. Also, on the inside of the firewall we did an access list that computers from staff vlan can access 1.1.1.1 on port 6552 (Which is the release spam port).Hence, we can release emails from internal network through the Microsoft Outlook.
 
On the outside network, we cannot release emails when using outlook web access.The host name for the PROXY release spam is proxy.domain.com so what we did also today is ask "ISP" to make an A record entry for another public ip which is 9.2.7.6 for proxy.domain.com.We meanwhile made an entry on the access list that comptuers from outside can access 9.2.7.6 on port 6552 (which is the release port).Now the only question is in regards to the static entries:
 
1. do we (and can we?) static map 9.2.7.6 to 1.1.1.1 through a port 3840 on the Cisco ASA (although we have already mapped 1.1.1.1 to 9.2.7.5 - I have a doubt here as this might mean we might not get emails? Or would we have to do the static again for this one specifcying the 9.2.7.5 as an smtp entry and the 9.2.7.6 as a release button?

2. have I made a mistake in general and should I have just told the ISP to make a CNAME entry for proxy.domain.com with the public ip 9.2.7.5 (which is the public ip for MX record?)?