MS SBS 2003 Fax Service fails to route fax to email

Fax Service on SBS 2003 stopped routing to a POP email account with no clear explanation. Got the following error:
Event Type:      Error
Event Source:      Microsoft Fax
Event Category:      Inbound
Event ID:      32089
Date:            9/30/2008
Time:            10:31:49 PM
User:            N/A
Computer:      MR-SBS
Description:
The Fax Service failed to execute a specific routing method. The service will retry to route the fax according to the retries configuration. If the retries fail, verify routing method configuration.
 Job ID: 0x0401c92373644e15.
 Received on Device: 'Brooktrout Line #1 (TRUFAX)'
 Sent from: '8668300484'
 Received file name: 'C:\Documents and Settings\All Users\Application Data\Microsoft\Windows NT\MSFax\Queue\1C92373644E15.tif'.
 Routing extension name: 'Microsoft Routing Extension'
 Routing method name: 'Route through e-mail'

For more information, see Help and Support Center at http://go.microsoft.com/fwlink/events.asp.
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I've seen some solutions that involved AV/AntiSpyware/SPAM blocking software, etc. . . . and am certain this isn't relevant here. The faxes are coming in and being routed to a folder without any trouble. It just won't go to the email. I have successfully reached an external mail server via telnet.