Indeed, a lead can exist in multiple lists, provided that it is added to them explicitely.
This means that your episerver integration only does it once, probably so that you can use the list to identify the lead source.
A lead certainly belongs to as many (static) lists as you want. This sounds like a bug in epi's connector.
Sanford Whiteman, @Grégoire Michel
I found an alternate solution in episerver which is much more in keeping with how marketo expects a lead to arrive from a form submission.
Episerver xforms allows us to set the form submit url, this can be set the the lead-capture/save url.
Provided the following are set marketo will see a lead (new or existing) with the correct filled out form activity:
- Empty/basic marketo form exist (for form id)
- Episerver generated a hidden field on a form for munchkin id
- Episerver xform block sets a hidden field option for marketo form id
- Episerver xform form submit url points to the correct marketo environment
- Episerver xform form field names match form field names in marketo