> A decent system should convert the received filenames instead.

As it's done today with any (functional) Zmodem receiver.

 > Say that all EMSI-II mailers must be able to receive any
 > filename and convert to the local OS if nessesary.

What does this have to do with a session negotiation/related protocol?

EMSI doesn't send files.

The FNC flag was (is) a mistake and it _will_ be removed from future EMSI
specifications. It is up to the receiver to handle filenames according to
its own capacity and limitations.

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