[Tracker] can't get email contents

[孤云独闲 <tomsunchen gmail com>]

Hi everyone:

    I came across difficult about t search email in tracker. I executed below command:
     #tracker-sparql  -q  "SELECT nie:url(?s) nmo:messageSubject(?s) nmo:from(?s) nmo:plainTextMessageContent(?s) WHERE{ ?s nmo:messageSubject 'wangzhi'}"
Then got below messages:
      email%3A%2F%2F1280907738.12500.1%40localhost.localdomain/%E7%BD%91%E7%AB%99/1206688162, wangzhi, urn:uuid:ff907c12-c984-c15f-2001-cdfbfe2f16f6, 



     email%3A%2F%2F1280907738.12500.1%40localhost.localdomain/%E7%BD%91%E7%AB%99/1206688163, wangzhi, urn:uuid:ebbd6c08-00b6-7875-9f32-5976c885be1a, 
    a. i want to get url  format  that  the evolution can open. but  "  email%3A%2F%2F1280907738.12500.1%40localhost.localdomain/%E7%BD%91%E7%AB%99/1206688162" is not what i want . why ? 
    b. i want to know  the sender and receiver email address(example for tomsunchen gmail com ) by nmo:from(?s) and nmo:to(?s). but that return "urn:uuid:ff907c12-c984-c15f-2001-cdfbfe2f16f6", how  i change it to email address?
    c. if i need to get the contents of email, what should i do ?  i found nmo:plainTextMessageContent is not indexed, nie:plainTextContent is indexed, whether nmo:plainTextMessageContent or 
       nie:plainTextContent, it always return nothing. why? what should i do ?
 
    if i execute below command:
    tracker-sparql  -q  "SELECT ?s WHERE{ ?o nmo:to ?s; nmo:messageSubject 'wangzhi'}"
   i think it should return  above information,but there is no result to return. why?

Thank you very much!

-- 
Best Regards,
tomsun