HI,
Hi Mamoon,
Thank you for contacting Aspose support team.
Aspose.Email can be used without installing Outlook. you may please visit following links to get more information about this product:
Regarding the support on Windows Phone 8.1, theoretically it should work as no such limitation is found in the documents. However you may please test it on the Windows phone by simple program like Creating a new PST and adding folders and let us know the feedback. I have also logged it under Id: EMAILNET-35048 for further investigation by the product team. I shall write here as soon as some feedback is received in this regard.