> Occasionally posts to this list contain a lot of extra baggage
> such as:
>
> ------ =_NextPart_000_01BD25C5.8BC30200   --,
> Content-Type: application/ms-tnef           }  A
> Content-Transfer-Encoding: base64         --'

> eJ8+IgEXAQaQCAAEAAAAAAABAAEAAQeQBgAIAAAA5AQAAAAAAADoAAEIgAcAGAAAAElQTS5NaWNy
> b3NvZnQgTWFpbC5Ob3RlADEIAQ2ABAACAAAAAgACAAEEkAYA4AIAAAIAAAANAAAAAwAAMAMAAAAL
> AA8OAAAAAAIB/w8BAAAAWAAAAAAAAACBKx+kvqMQGZ1uAN0BD1QCAAAAAHBpYyBtaWNyb2NvbnRy
> b2xsZXIgZGlzY3V .... and so on for dozens of lines.

> Evidently the above contains another copy of the message in
> MIME(?) format.

Technically, MIME is used to separate the parts of the message.
It also describes the encoding format for binary objects (the
MS-TNEF part).  It consists of the 3 lines (marked A above).

The actual part content, "dozens of lines", which bloats the
message is Microsoft specific.

> The common denominator seems to be Microsoft mailers.

You betcha.  MS-TNEF is Microsoft Transport Neutral Encoding
Format.  It's a binary blob used and useful only to people
running Microsoft's email products.  Microsoft assumes everyone
needs these and emits them by default.

Microsoft Exchange is at least properly encapsulating them.
Prior to MIME, they used uuencode and stuffed their binary
object at the end of the text (remember winmail.dat?).


> If anyone knows where the magic switches are

Sorry, I don't.
                                                Lee Jones