I see using the property WebClientReadFormQueryString we can get the OWA URL to the email message but how can I get the OWA URL for each FileAttachment?

Hi Gary,

Returning OWA URL for attachment preview isn't supported in EWS, and there are no plans to add this.  For Office 365, we do have plans of adding this to our REST API, but I don't have a timeline to share. What is your scenario requiring OWA attachment preview URL?

Thanks,
Venkat

Thank you for the reply Venkat.  

We use the EWS API to get mail and attachments for search appliances like Google and FAST and a few others.  The content is then converted to a feed since most appliances cannot crawl Exchange.

Currently we use the OWA URL for the email message that contains the attachment when the the user performs a search.  It would be much nicer if we could provide the actual URL to each attachment.  I had seen one method using WebDav (PROPFIND on X-MS-ENUMATTS) but I'm not sure this is even supported for Exchange 2010/2013.

Gary