Heh, neat to see this on here. I was the one who actually wrote vvmd and VVM player for Linux Phones (Plasma Mobile intends to use vvmd as a backend, if you look at the issue tracker referenced).
It was a bit surprising to me too to see how IMAP is used, but it also made it pretty easy to write the program to add in support. Writing a GUI I thought was much harder.
Do you know how authentication works for this client?, does the carrier verify mobile number by using network information?
Prolly receive the PIN through binary SMS.
Everything is in these binary SMS's
Bring backs memories when I wrote an Android Visual Voicemail for a telco.
Fun fact, iOS couldn't do this as they have contracts with other telco's.
Navigating through these folders wasn't that great tho.
Setting your voicemail message by uploading an AMR file in a special folder was rather hacky.