Its been a long while since my pre-Casper ARD using days. but I do think this is possible to do, with some caveats, and provided your users are logging into their Macs with AD accounts and not local ones. (If they're using local accounts, then you don't need to read any further, since I don't think there will be a workable solution)
If the users are logging in with AD accounts, the pertinent information about their accounts, such as name and email address among many others, gets stored in the local directory node with their cached account.
Since ARD can send a shell script to your Macs, you could send a script that would pull this information from the logged in account, or, if no user is logged in, then from the most common user listed in the 'last' command., and then query the local directory for the email address and echo that back.
ARD can send script output back to your console in a text window, so after the script completes you should have a list of email addresses from whatever it could pull.
Usual ARD caveats apply though, in that if a Mac isn't powered on, you can't pull anything from it. As such, you may need to run the script multiple times over the course of a week or so, and merge all the results.
If you need some help putting something like the above together for testing, just post back.
thank you so much, i will take a look at this and see what kind of script I can use to do what you explained 
Some users are bound and some are local accounts, however it think it would help a lot to at least get something started, I will follow up on this!
Something like the below should work:
#!/bin/sh
# HARDCODED VALUE FOR "loggedInUser" IS SET HERE
loggedInUser=""
####################################################################################################
#
# SCRIPT CONTENTS – DO NOT MODIFY BELOW THIS LINE
#
####################################################################################################
loggedInUser=`/bin/ls -l /dev/console | /usr/bin/awk '{print $3}'`
accountType=`dscl . -read /Users/$loggedInUser | grep UniqueID | awk ‘{print $2}’`
if (( "$accountType" > 1000 )); then
userRealName=`dscl . -read /Users/$loggedInUser | grep RealName: | cut -c11-`
if /> -z $userRealName ]]; then
userRealName=`dscl . -read /Users/$loggedInUser | awk ‘/^RealName:/,/^RecordName:/’ | sed -n 2p | cut -c 2-`
fi
userEMail=`dscl . -read /Users/$loggedInUser | grep EMailAddress: | awk ‘{print $2}’`
if †-z $userEMail ]]; then
userEmail=`dscl . -read /Users/$loggedInUser | awk ‘/^EMailAddress:/,/^FirstName:/’ | sed -n 2p | awk ‘{print $1}’`
fi
Taken from a larger script of mine: http://macmule.com/2012/05/16/submit-user-information-from-ad-into-the-jss-at-login/
So how could i deploy this via ARD? kind of a noob with scripts :(
Via the "Send UNIX" command.
Find a test mac & login with an AD account then try.
Yeah i pretty much copied and pasted what you posted into ARD to a system thats mine and tried to send it to see what would happen but it kicked back an error.
grep: write error: Broken pipe
/bin/bash: line 27: syntax error: unexpected end of file
I've never used ARD, but according to https://www.apple.com/remotedesktop/assetmanagement.html it allows you to pull user history reports. If you can pull a good user history report, you could just put the users into an array and utilize @bentoms script to output the results to a .csv file, which could then be sent to your Exchange admin. Another thought that comes to mind is to use your company's asset management database to pull the report, assuming there is one in place.
if (( "$accountType" > 1000 )); then
userRealName=dscl . -read /Users/$loggedInUser | grep RealName: | cut -c11-
needs a "fi" after it
Im trying the user history report thing... never even knew it was there lol... amazing.
