I have tried utilising this with Outlook Web Access 2010 (Version: 14.1.270.1).
The link.txt file can be amended successfully to read (for example) https://owa.mydomain.com/owa/?ae=Item&a=New&t=IPM.Note&to=%RECI%&su=%SUBJ%&body=%BODY%
In this case, a new email in OWA does successfully get initiated, BUT ONLY IF AN OWA BROWSER SESSION HAS ALREADY BEEN AUTHENTICATED. If the user has not already logged into OWA successfully, OWA generates the following (example) error message:
The mailbox you requested couldn't be opened because no match was found for the address "?ae=Item&a=New&t=IPM.Notefirstname.lastname@example.org&su=&body="
. Make sure the address is spelled correctly. If the problem continues, please contact your helpdesk.