🚀 go-pugleaf

I have always believed that the general rule for implementations is
that they should expect the least from other implementations, and
be as robust as possible, as far as conformance to a given RFC is
concerned.  With that thought in mind, I have a question for TCP-IP
implementors who have done SMTP implementations.

Given a permanent error condition and that you control SMTP server
code, which do you believe to be the better action?

[a] Immediately have a server respond with an error to the SMTP client
    leave the client to report the error.

[b] Receive the message and report the error directly to the sender.

Solution [a] is the straight forward method which programs such as
most incarnations of sendmail use.  I know of at least one
implementation that has used solution [b] in the past.  The reason for
using solution [b] is that I would not have to rely on any other
implementation to properly dispose of the error.  I have heard of at
least one implementation that considered a particular permanent error
response as temporary, and the fact that it was blatantly wrong didn't
stop it from continually retrying our host.  Using solution [b]
eliminates such bizarre cases, but places honus of error handling on
the server.

What's your opinion?
-- 
Eliot Lear
[lear@net.bio.net]