sending mailing list with smtplib

[3KWA]

3KWA wrote:
> Just for education purposes  (mine I guess :P) what was the idea behind
> that design decision?

>From the doc (self education :P)

The following methods implement a mapping-like interface for accessing
the message's RFC 2822 headers. Note that there are some semantic
differences between these methods and a normal mapping (i.e.
dictionary) interface. For example, in a dictionary there are no
duplicate keys, but here there may be duplicate message headers. Also,
in dictionaries there is no guaranteed order to the keys returned by
keys(), but in a Message object, headers are always returned in the
order they appeared in the original message, or were added to the
message later. Any header deleted and then re-added are always appended
to the end of the header list.

These semantic differences are intentional and are biased toward
maximal convenience.