Unable to retrieve ‘sender’ from mail message

[cnbatch]

When the mail was sent from a mailbox by another user (aka ‘on behalf of’, like ‘A@c.com on behalf of B@c.com’), ews-cpp cannot retrieve the ‘sender’ (A@c.com) section on this mail, ‘sender’ shows blank when get_sender().value() was called. Only ‘From’ (B@c.com) section can be retrieved.

In Microsoft's EWS Managed API, ‘sender’ can be retrieved correctly.

Exchange Server's version read by MS API was Exchange2003 SP1, the same as ews-cpp set in the code.