Search-Mailbox -SearchQuery not working as expected

I want to find messages with the exact subject "eFax Report", not subjects containing the word "eFax Report".  I've tried all of the following search querys and get the same results which include subjects such as "FW: eFax Report","Aug eFax Report", ect. 

Any ideas?

Search-Mailbox -SearchQuery {Subject="eFax Report"}
Search-Mailbox -SearchQuery {Subject:"eFax Report"}
Search-Mailbox -SearchQuery 'Subject="eFax Report"'
Search-Mailbox -SearchQuery 'Subject:"eFax Report"'