Some of our clients have been experiencing this issue for a while and we thought that iOS 6 may have been updated to fix the issue. However, here is our workaround. Bear in mind that this isn’t an Apple authorised fix or are you guaranteed that by following our advice in the below notes will be perfect.. so go forth at your own risk!
This problem applies to those of using Exchange ActiveSync™ account set up on your iPhone for email.
You Reply or Forward an email directly on your iPhone, your iPhone shows the a Reply or Forward icon status, but when you then check your Mac desktop’s Apple Mail the Reply or Forward status has not been synchronised.
Why this happens:
There is a bug with ActiveSync™ version 12.1 which is that function that is used when a iPhone’s email account is setup using MS Exchange. Apparently this ActiveSync™ bug has been fixed in version 14 but at this time (iOS 6.01) Apple have not implemented the ActiveSync version 14 (not sure what happened to version 13).
Instead of setting up the iPhone as Exchange an Exchange account, re-setup the iPhone using IMAP.
If you need Calendar and Contact synchronisation then you also setup CalDAV and CardDAV accounts.