If you have CRM for Outlook installed and try to print an email you might see this:
This BOYUMGUID is a sideeffect of CRM for Outlook due to the Tracking functionality (we need a unique identifier per mail).
The field itself is Outlooks equivalent of User Defined Fields in SAP. It is great that Outlook have such a feature but what is not so great is that Microsoft for some odd reason have decided that such fields by default need to be part of the printout and worse, that it is not something that can be customized :-(
We are looking into potential workaround (aka if there is some way we can hide it in the printout) but so far we have not found a way to do it
Should we find a way down the road we will implement it