When you try dialing out on an analog line that has voicemail tied to it, the AccelePort RAS will not recognize the initial tone you get indicating a voicemail message and will report "No Dialtone".
The AccelePort RAS is looking for the standard dial tone and because of the initial difference in tones isn't able to determine that a phone line is connected.
You will have to add an X3 before the dial string to inform the AccelePort RAS not to look for a dial tone.
For example, to make an outbound call with Hyperterminal you would type:
AT X3 DT5551212
NOTE: You can find the AT Command set for this product from the document AT Commands for the Dense Modem Family or you can look it up at the Digi Support Site.