Inbound action create incident (forwarded) need to set caller id from user who forwarded it first

[Rob96]

I have a requirement to create an incident from a forwarded email which has been forwarded twice. It needs to set the caller field to the original user who forwarded it. Email address of user is the user id.

I've tried a few permutations but not working. The account that forwards to ServiceNow is a user so in our Dev instance I have made that user inactive so that user is not set as caller, but all that happens then is the incident is logged as guest.

[Mark Manders]

What happens to the first email coming in? Where is the email coming from? How do you recognize it as being the second one? 

[Rob96]

The first email is initially sent from a separate application as an alert to a user. This user will normally have a user account  on the ServiceNow instance. This is the user I wish to set as caller. The user then forwards the email to an internal team (this team has an account also on ServiceNow but it is inactive). If the internal team thinks it warrants further investigation they will forward it to the ServiceNow instance. Hence 2 forwards and I want the first to recipient (or first forward from which will be the same).

[Mark Manders]

I am probably missing something here. This doesn't make sense.

Why not create a ticket from the first email and have the system forward the email to the team. They can reply and just let the system update the ticket.

[Rob96]

Mark I understand that and I know that would work, but it is not an option as it would bring inconsistency to the reporting methods the users already use.