Corelight - SMTP Email containing NON Ascii Characters within the Subject

Original query, unchanged.

corelight_smtp
| where subject hasprefix @'\=?utf-16'
| mv-expand to_recipient = todynamic(to_) to typeof(string)
| summarize recipients = dcount(to_recipient)
| extend k = 1
| join (corelight_smtp
        | where subject hasprefix @'\=?utf-16'
        | mv-expand to_recipient = todynamic(to_) to typeof(string)
        | summarize by to_recipient
        | extend k = 1) on k
| where recipients > 1