The message you are getting can arise from a number of causes, but I think the most common one in the past few years would definitely be AntiVirus software blocking TCP port 25. The 'bad ol days' when we used to see mass-mailing worms with their own SMTP send engines led to most AV vendors making blocks on TCP25 a default setting for their products. CallPilot uses this port as it's client to server conduit for facsimilie transmissions.
If this is your particular issue, there are two ways of getting around this; open TCP 25 on your antivirus software (maybe not the best idea), or change the port which CallPilot uses to Secure Layer SMTP (SSL). You can find the setting for this in the client through the CallPilot Service property sheet (or just right-click the root of your CallPilot mailbox and choose 'Properties'... 'Advanced'... 'Mail'... 'Advanced') and turn on SSL for both IMAP and SMTP.
There is a corresponding setting you must enable in the CallPilot server to support the secure layer ports: In the CallPilot Manager web applet choose 'Messaging'... 'Message Delivery Configuration'... 'Security Modes for SMTP Sessions' (note - can be hard to find as it is just a hyperlinked piece of text on the MDC page)... and turn on the SSL options there.
The second posibility is that the CallPilot server address/ name (if using FQDN must exactly match what is configured at CP server), and or SMTP/VPIM information are not correctly configured at the client.
Cheers,
C