So to clarify, "forwarding" here only refers to full automatic forwarding of one address to another, not manual Fw: right? I can't imagine they'd break the latter
“Forwarding” here almost certainly refers to the From: header in the email. If I receive an email at my personal gmail address with “From: noreply @mybank.com” that was sent to me by “myuniversity.edu”, gmail will start to mark that email as nondeliverable because the message “claims” to come from the bank. But this might be a normal setup. Perhaps my bank has my university email address, and my university mail server is configured to pass the email along.
Clicking the forward button merely copies the email body into a new message appearing to come “From:” your personal email address, so there isn’t an issue with that. Doing this doesn’t preserve headers however.
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So to clarify, "forwarding" here only refers to full automatic forwarding of one address to another, not manual Fw: right? I can't imagine they'd break the latter
“Forwarding” here almost certainly refers to the From: header in the email. If I receive an email at my personal gmail address with “From: noreply @mybank.com” that was sent to me by “myuniversity.edu”, gmail will start to mark that email as nondeliverable because the message “claims” to come from the bank. But this might be a normal setup. Perhaps my bank has my university email address, and my university mail server is configured to pass the email along.
Clicking the forward button merely copies the email body into a new message appearing to come “From:” your personal email address, so there isn’t an issue with that. Doing this doesn’t preserve headers however.
Yes, that is correct. In my job I started referring to this as 'relaying', to prevent confusion with forwarding (Fw:) from an email client.
In more technical terms: in the article they are talking about forwarding on the MTA level, not the MUA level.