Add x-original-to to feed sources for mapping

Hi there,

I have a situation where the "to address" is set to "undisclosed-recipients:;" which gives me an empty field after Feeds mapping into a text field.
On my Squirrel mail server, I can view the full header of the email and although the "To" is indeed set to "undisclosed-recipients:;", the information I am looking for is present in "X-original-to". Unfortunately, among all the available sources in Feeds mapping, there is no "X-original-to". I have tried to use BCC or CC info but there's nothing in those.

Would it be easy to read the X-original-to" from the email header and make it available as a source for feed mapping? Any help on the code I should add or the code I should look at to get inspired would be appreciated :)

Thanks !