ews_to_owa_id.rb

# To link to OWA from an EWS item_id you must first convert the ID to something OWA will understand.  You can do it using the following.  After that, open the item like so:
# https://host/owa/?ae=Item&a=open&id=<converted item id>

$: << 'lib'
require 'viewpoint'
vp = Viewpoint::ExchWebServ.instance
vp.authenticate
vp.find_folders
msgs = vp.get_folder('Inbox').get_todays_messages
msg = msgs.last

altids_ar = NonEmptyArrayOfAlternateIdsType.new

altid_t = AlternateIdType.new
altid_t.xmlattr_Format = IdFormatType::EwsId
altid_t.xmlattr_Id = msg.item_id
altid_t.xmlattr_Mailbox = "[email protected]"

altids_ar.alternateId <<  altid_t

convertid_t = ConvertIdType.new(altids_ar)
convertid_t.xmlattr_DestinationFormat = IdFormatType::OwaId

resp = vp.ews.convertId(convertid_t)
owa_id = resp.responseMessages.convertIdResponseMessage.first.alternateId.xmlattr_Id
uri = "https://host/owa/?ae=Item&a=open&id=" + owa_id