Is it possible to query EV to pull Exchange Message IDs? Either through SQL queries, API, etc.?
This post implies that attribute is indexed via the "iden" attribute:
How can I pull this data from EV?
if you're using EV 10 or earlier then you can do it exactly how that URL describes. if you're on EV 11 then you can do it too, just need to go to the advanced search within EV Search and enable the additional attributes with an extra click.