There are several ways Crozier could have and should have conveyed any of his concerns. An unclassified memorandum is not one of them. Not ever. Here are just two examples that would have been proper. Crozier could have sent Baker a Navy message referred to as a “P4.” The subject line actually reads “Personal for (name).” A P4 message is an attention-getter. They are often used to address sensitive matters without alarming everyone because the distribution is between the sender and the recipient. Think of a P4 as the functional equivalent of grabbing someone by the lapels and saying, “This is really, really important!” When I was the flag lieutenant to a three-star admiral, a P4 message got immediate attention.
If Crozier was truly concerned about the coronavirus and believed the entire Navy chain of command deserved notification, then he should have sent a casualty report (casrep). A casrep is a formatted Navy message used to document significant materiel and personnel readiness concerns. A casrep message from an aircraft carrier, particularly one that is forward-deployed, would get the attention of the entire defense establishment. When I served on the staff of a fleet commander, every casrep was briefed to the four-star admiral. There was an all-hands-on-deck effort to immediately resolve the matter. In the words of Joe Biden, “This is a big f***ing deal.”
Crozier used unsecured communications. He transmitted what is arguably at least For Official Use Only, if not classified, information over an unclassified medium. Nothing more needs to be said about this.