I tried to manually execute the following in Apex Anonymous and the result is returning NULL Case ID. Does anybody know how to use the new case header method?

  #Email #Customer Service #Email-to-case #Case #EmailMessage Object

Apex Anonymous 

List<Messaging.InboundEmail.Header> headers = new List<Messaging.InboundEmail.Header>();
Messaging.InboundEmail.Header messageHeader = new Messaging.InboundEmail.Header();
messageHeader.Name = 'Message-ID:';
messageHeader.value = '<BLAPR16MB37478D93BEC69718C9576BEBBF089@BLAPR16MB3747.namprd16.prod.outlook.com>';
headers.add(messageHeader);
Id caseId = Cases.getCaseIdFromEmailHeaders(headers);
System.Debug('JOSEPH DEBUG : caseId ' + caseId);

RESULT

15:39:52.1 (7718512)|SYSTEM_METHOD_ENTRY|[11]|System.debug(ANY)

15:39:52.1 (7727733)|USER_DEBUG|[11]|DEBUG|JOSEPH DEBUG : caseId null

15:39:52.1 (7735978)|SYSTEM_METHOD_EXIT|[11]|System.debug(ANY)

When querying for the record in the EmailMessage for that Message-ID, it exist in the EmailMessage object.

SELECT Id, Headers, Subject, MessageIdentifier, ThreadIdentifier, ReplyToEmailMessageId, ParentId, ActivityId, ToAddress, FromAddress 
FROM EmailMessage 
WHERE MessageIdentifier = '<BLAPR16MB37478D93BEC69718C9576BEBBF089@BLAPR16MB3747.namprd16.prod.outlook.com>'