Re: 2 MIME questions re: message/rfc822

> > no.  you shouldn't be expected to hide useful information for the 
> > recipient just so that the mail system will be transparent.
> Agreed. But IMO, the list processor software is a recipient as far as 
> the internet mail system is concerned. (You get a final delivery DSN 
> when the message is delivered to the mailing list processor.)
okay, I'll grant that.  but if the list processor is going to alter the 
message, it needs to consider the effect this has on digital 
signatures.
> > there are plenty of reasons for looking at a message to decide 
> > whether to bounce or filter it.  there are far fewer valid reasons 
> > for altering a message.
> Converting to internal format and then back can transform invalid 
> input into valid output. Is that bad?
in general, yes.  the goal of the mail transport (even of lists, IMHO) 
is not to produce "valid" output, but to convey the message that the 
sender sent.  for instance, MTAs that alter dates because they are not 
invalid format can cause the message to appear that it was sent at a 
different date and time than it really was.