question on using qmail for voicemail

Hi Folks,
   I have implemented a voicemail sub-system for a SIP distributed VoIP
phone system. Voicemail messages are converted to email messages with audio
attachments and sent to qmail. All this works great, users can use the phone
system qmail client to listen to messages on phones or can listen to
voicemail using the PC and a mail client of their choice. The challenge is
to get the mail server to tell the voicemail sub-system when a message has
been read so I can turn off the message waiting lamp on the phone. I noticed
(on the linux distribution that I am using) that qmail stores new user
messages in a directory called MailDir in one of three folders (new cur
tmp). My voicemail system could poll the new directory and turn off the
light when it's empty (yuk). 

Is there a better way???

..FG..