is there a clean way to find out the names of the Postoffice and the
Domain using SOAP (or the full GroupWise-style name of the user) ?

I'm still with my archiving application (fetching the messages as MIME
through IMAP). I now hav a customer, that disabled the address format
userid@domain in the Internet addressing settings - and I can't login
with the pure userid to IMAP anymore.
But I found out, that one can allway login to IMAP with
USERID.POSTOFFICE.DOMAIN. Now I need to find out the names of the
postoffice and the domain with SOAP.
(I know that they are embedded into the folderID, but I don't belive
that I can rely on this..)