Resolution.

MS Office / Outlook 64 bit is not compatiible with the IPSentry MAPI libraries.
See: http://office.microsoft.com/en-us/outlook-help/choose-the-32-bit-or-64-bit-version-of-microsoft-office-HA010369476.aspx

IPSentry is a 32-bit ap[plication (x86). Use of the Exchange MAPI capabilities requires Outlook 32-bit.

The only workaround would be to utilize SMTP / POP3 and bypass MAPI if Outlook 64 bit is required to be installed.

Thanks to the OP for identifing this issue.