A recent bug report has highlightled that the Interim Fix 1 (IF1) for IBM Traveler causes an issue in where email sent from the devices with Traveler installed are not actually delivered.
This issue is only relevent for upgraded servers to Traveler 18.104.22.168.
In order to allow emails to be sent you simply need to revert back to the previous version of Traveler (22.214.171.124) whilst IBM look to fix the fix!
You may also need to remove and re-install the Traveler profile on the device.
If you need any help with reverting back to a previous version or any upgrade and installation help please get in touch and we'd be happy to help.