My wife had some image mail attachments that were stored in aspx form. I suspect they were holdovers from a much earlier computer that could deal with them. A current Mac running 10.11.6 can't. Changing the extension to pdf or trying to open them in Safari doesn't work either. What does work is to open them in LibreOffice and copy and paste them to an rtf document in TextEdit. From there, an individual image can be dragged to an outgoing mail file or used in any other way.
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