There is one serious problem with sending out 8 bit mail. If the receiving MTA does not advertise 8 bit MIME you have to transcode in the MTA. A few MTAs have decided that buggering about with message bodies like this is not in their purview and therefore do not advertise 8 bit MIME by default since then any mail they relay might then have to be transcoded to 7 bit. A case in point here is exim which does not do MIME transcoding (or body hacking in general).
If you do have an 8 bit message, and are trying to send to a non 8 bit recipient MTA, and will not transcode, you then have a problem. You can then either just send it (sod you, take this anyway) or bounce it.
For this reason a case could be made for all mail initiators, including MLMs, to encode for 7 bit transport.
Its a shame SMTP wasn't originally defined as an 8 bit channel.
Nigel.-- [ Nigel Metheringham Nigel.Metheringham@InTechnology.co.uk ] [ - Comments in this message are my own and not ITO opinion/policy - ]