Ok, the imap storage for asterisk voicemail works like the proverbial charm. I needed some work on the home dialplan and setup before I could test it, but I was able to leave a message to the home mailbox, seeing it stored in the voicemail imap box and retrieve and delete it using a telephone connected to the ISDN port accessing the VoicemailMain application. The access number for voicemail is now set to 0140-1233 to (sort of) stay in line with the Dutch numbering plan. There is no customer-service at 0140-1200 planned...