Windows Mobile is the only mobile device range which is not cheatable with the man in the middle SSL-Spoof.
IOS 5 and current Android may be unsafe currently if you use self signed SSL Cert for the Activesync IIS Site.
Explained For non IT-managers (people who pay IT people and reduce their budget)
1) If you are a Small Business 2) You run Exchange 2003/2007/2010 SBS 3) You don’t want to invest in a official SA/UC certificate 4) You internal Administrator has come up with an inexpensive solution of Self Signed SSL (because you dont’ want to spend USD 300.- per year) 5) Your employee visits a hotel or meeting room with a faked free WIFI (A hacker does a man in the middle split). He checks mail with his Iphone. 6) The IPHOEN or Android connets to the fakes exchange / the hacker sniffs the traffic. 7) Hacker sens Remote wipe signal 8) Your mobile data is gone
http://www.wpcentral.com/windows-phone-dodges-black-hat-2012-certificate-vulnerability
http://www.blackhat.com/usa/bh-us-12-briefings.html