When an unassigned email is Ignored or marked as Spam, it’ll end up in your Trash.
Hovering over an item in your Trash will show you who deleted the email and when it was deleted.
Emails that don’t have ignored data, for example auto-responders, won’t show who ignored them.
In addition, emails ignored by an Automation won’t show who ignored them as it wasn’t a rep who ignored the email.
Note that any emails ignored before late March, 2019 won’t show who ignored them.