I am not sure if I can help. That email is sent out by our underlying telephony engine (Asterisk), and when I have a look at their
source code, it looks to be constructing the message OK to me.
Given that it works in the normal Outlook app (and loads of other email clients) I can only presume that it is a deficiency in the way the Windows Mobile email client works. Sorry I can't help more.
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Craig