bug#2942: rmail unable to get new mail from a Babyl file

[Glenn Morris <rgm@gnu.org>]

Severity: serious

Let `foo' be a Babyl format mail file:

emacs -Q
C-u M-x rmail RET foo RET

works fine. The individual messages are processed correctly.

emacs -Q
M-x rmail RET
C-u g foo RET

does not work correctly. Emacs says "No mail".

If the RMAIL buffer was empty originally, the raw Babyl file is dumped
into the buffer.

If there was mail originally, there is no apparent change in the RMAIL
buffer, but the Babyl file is invisibly appended to the end of the file.


At the least, Emacs should refuse to get new mail from a Babyl file if
it cannot handle it. Preferably, it should be able to handle it.

(This is unrelated to the latest Rmail changes.)