From the Outlook for Mac forum on Microsoft Answers:
From a little time, I have this problem. Some messages are with strange characters. Here an example, but sometimes a messages contains a lot of characters like that. The word is HCI and then there is a S with an accent !!!
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Continue Reading: Avoid strange characters when sending mail through Exchange or Office 365
A simple method is described for allowing the easy insertion of subscript and superscript characters into an entourage message window – either plain text or HTML! . . .
Continue Reading: Using SuperScript in an Entourage Message