[jumpbrick]

Although...if the sender was (possibly unknowingly) using the employer's WiFi...they could have a much easier time tracking them. Also, the IP addresses in the email chain could give away their location (for instance, if there is only one employee in a certain country). Not saying that it isn't a bluff, just that it's possible they know more than is obvious.

I've never seen an employee that wasn't replaceable, and that includes managers. But without a doubt, anybody that would send an anonymous email is the first chicken-shit to go.

Added after 10 minutes:

I am curious:

Using the same logic that says it is impossible to trace the phone number (and often the IP address) of an incoming email, how could they know it came from a phone?

I suspect there is more information than we are being given (possibly in the body of the email). Or, maybe it came from an email address the user associated with EE (easy to look up the owner of a legit email server), and their phone number shows up in the email address or a boiler plate signature? Just guesses.

Maybe YOU have special knowledge that it came from a cell phone. Were you the sender?