In a message to rowan crowe 
Neil J Marshall  wrote:

 > I have always programmed on the understanding that MSGID lines
 > are case insensitive, just as to and from names are, Area Tags
 > are, Domain Names are and so on.

No, the data contained in MSGID lines must remain identical to how it left
the originating system.

 > Otherwise no-one in FIDOnet (or fidonet or FidoNet or any other
 > way it is capitalised) would ever be able to recognise each
 > other's messages when Domains are included, for example.

The purpose of MSGID/REPLY is to aid duplicate message detection and
provide a method to base reply linking upon.  MSGID/REPLY lines should not
be used to obtain addressing information, this was not their purpose.

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