It looks like it is also an String Array:

System.String[]

Instead of just a String:

System.String

I am not familiar with this broker; how is this data returned perhaps using the SmartObject Service Tester tool?

Tin:

Thanks for the reply.

I spent awhile on a phone with a K2 person today trying to figure it out and we did not have luck.  

We tried converting the value to a string and that didn't work.

In the smart object service tester, the return values look normal:

Thoughts?

Well, I gave up on this.  

I ended up bypassing workflow and just using smart forms to do a list method against the "list emails method" on the smart object, and then a "for all items in list view" writing the results of the list to the database.  The only downside is that it's no longer running on a schedule, rather the end user has to press a button on the form to have the mailbox update in K2, but in some ways that's better as it's now on demand rather than on a schedule.  

I'm still puzzled why these items pull in perfectly into a list view, but do NOT do the same thing using the "create reference" in workflow (isn't that more or less the same thing?) but I'll write it off as yet another "K2'ism" and move on.

Thanks for everyone's help.

Rob