This will happen if you clicked through from a sample email where you aren't impersonating a lead.
I assure you this is not the case, this just started happening today.
I need this fixed now
This is happening to several others, as well. See View as Webpage does not work: "Customer does not belong to any POD"
I would recommend contacting Support to make sure they are aware and can look into it.
I think it's a global issue in Marketo. It happened to us today only - was working fine yesterday.
Support is rolling out the patch to fix the issue -
This started happening for us as of today. Would appreciate notice before things like this are going to happen. Can y'all please fix this as soon as possible
We're having this problem too.
they fixed it. It's working now.
I've noticed that this tends to happen when an email is edited and re-approved after its already gone out, even when sending samples.