Do I have to have email address for PURLs?

I'm trying to export a list I imported into Marketo to use PURLs on a mailing for a Marketo landing page. I've exported PURL lists in the past. Every time I export I get an error saying the export was abandoned and to contact support (still waiting to hear). The list exports normally fine, but when I do a PURL export I get the error.

I don't have email addresses for the list. Is that a must-have for a PURL list export? If so I don't understand why.

We are sending them a direct mail with a PURL to a MKTO page for a VIP event they can register for which is where we will gather their email address and other data points.

Any ideas? What am I missing?