Not that I am aware of. Here is the problem. UM uses Microsoft Exchange as the information store for voice mails. That means that unity does not store any of the messages locally. When you play a message through unity, it actually connects to the person's e-mail inbox to the wav file. If it sent a message without the attachment, the voicemail simply wouldn't exist.
It is what it is!!
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A+, Net+, I-Net+, Certified Web Master, MCP, MCSA, MCSE, CCNA, CCDA, and few others (I got bored one day)