Flow confusion -- downstream errors reported as upstream

[gene-hightower]

Describe the bug
There are error messages in outbound/hmail.js that refer to downstream servers as "upstream" servers.

Expected behavior
As I understand the flow of streams, it is from upstream to downstream, in accordance with gravity.

[baudehlo]

I picture it like this: External <-> Haraka <-> Internal (e.g. IMAP server).

In that picture, downstream is the IMAP server. Upstream is outbound.

[gene-hightower]

Any particular message (unique Message-Id) flows in only one direction.

[gene-hightower]

That flow should be shown in the Received: headers added to the message at each hop.