MAPI mail properties for backup

[velu5]

Hello,

I've got a query on the mailbox brick level backup using MAPI. The
intent here is to backup all the mails that the newer than the old
backup : I've been using the following three MAPI properties to
identify if its a new/changed item. These 3 properties are compared
with last backup time and if any one of them is later/greater than the
last backup time then it qualifies for a backup

PR_CLIENT_SUBMIT_TIME
PR_LAST_MODIFICATION_TIME
PR_MESSAGE_DELIVERY_TIME

Problem:
This logic holds good for almost 2-3 exchange servers that I've
tested, while in an particular exchange server it fails and turns out
that PR_LAST_MODIFICATION_TIME property is the clear distinguisher as
to which is the latest.

What the properties that should be considered in this case ?
Is a MSDN article or any MAPI sample code for doing the same?

Pls help on this regard.

Thanks in advance,
atvelu