There is a backward incompatibility with Message.get()
in the standard rfc822 module.  I don't believe this 
incompatibility is intended to be introduced, so here
is a bug report.

In Python 2.2 and later, Message.get("foo") returns
an empty string if the header field "foo" is not
defined.  In older versions of Python, on the other
hand, it returns None.

In fact, the definition of the method is duplicated
in the Message class in in Python 2.2 and later, as
follows:

class Message:

    def getheader(self, name, default=None):
        ...
    get = getheader

    ...

    def get(self, name, default="")
        ...

A possible fix would be to omit the later definition.

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You're so right.

I'll delete the "def get(...)" version both in the 2.2 branch and 
in the head of CVS.

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The documentation has not been completely updated.  The
default value returned by get() is said to be None at one
point and the empty string at a later point (when the
mapping interface of Message objects is discussed).  

Here is a patch (sorry, I cannot attach it -- no such field
in the SF interface??): 
http://arigo.tunes.org/librfc822-diff

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Reopened and assigned to Fred for doc bug.

(Armin: you can't attach files to an issue created by
someone else -- unless you're a project admin.)

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Committed Armin's patch and adjusted some nearby markup in
Doc/lib/librfc822.tex 1.43 and 1.38.14.4.