Sending a fax number in CFMAIL "to" variable

We're using Exchange, and I can submit an email through exchange fine using CFMAIL.  However, I need to format the "to" variable to be like:

to="[fax:7025551212]"

However, coldfusion is bouncing this email from the queue.  When I look at the email file, the "to" is blank.  Is there a way to format this fax number to allow CF to allow it fine.  Once it gets to Exchange, we have code that will automatically send it out as a fax.

Thanks!