Email settings: won't send but can't change!

Hi All,
I've deployed ADM on several machines at the office, and generally works well. Unfortunately, running into two issues that I can't solve!
The first is that, although most PCs here (all Win 7 pro SP1) can send alert emails, some cannot. The same parameters are being used (TO address, smtp server and settings), but some PCs simply refuse to send the test emails. I have turned off Win firewall, but have not yet found the commanilty that is blocking it.
The second: on a new PC I just installed, I encountered the same issue as above. I tried playing with different settings, but whenever I close the ADM and reopen it, the same SMTP settings return – I can't reset the SMTP settings entirely, and fear that it's trying to send using the original settings, even though showing something else onscreen.
I've further tried uninstalling ADM (several times), deleting the Acronis folder in Program Data, cleaned registry entries with ccleaner and manually in RegEdit, restarted and reinstalled... and yet the same email (and SMTP) settings persistently return.
Where is it storing this data so i can wipe it clean, and try again?
Thanks for your insight!
D #goingcrazy