2. RFC-821 describes a mechanism for transporting a message with a line with
a single "." in it. Putting that in rfc-821 now looks wrong. The correct
approach is for rfc-821 to say "this mechanism can only be used to transport
messages in which a single period on a line by itself is encoded away or
is not allowed." ...
Why should 821 impose such a restriction? Transport mechanisms, like SMTP,
in principle should transport arbitrary bits. In practice, they are a bit
more limited, but those limitations are bugs, not features. We need fewer
of them, not more.
If a transport mechanism is allowed to say "I will transport only messages
in a format that does not give me indigestion", then a message must meet
this criterion *for every transport mechanism it passes through*. Bear in
mind that rfc-822/rfc-xxxx mail may pass through more than one transport
system before reaching its destination, and the sender cannot easily
predict which ones will be involved (indeed, it may change dynamically).
Given this, requiring that the sender observe arbitrary transport-imposed
restrictions is a terrible mistake. We already have to live with some
of this; the last thing we need is more.
Henry Spencer at U of Toronto Zoology
henry(_at_)zoo(_dot_)toronto(_dot_)edu utzoo!henry