On Fri, 26 Aug 2022, Bogus User wrote:

Example, uploading email to a "magic directory" that forwards it.

Email transport over FTP used to be a thing actually;
though not exactly in the way you described. (In my understanding, mail-over-FTP was the main way of sending email to
another host in ARPANET era, before SMTP came along)

Back in the day, there were two ways of doing this:

A. Issue `MAIL` command on FTP control connection, then put the mail, line-by-line on that very control connection, and terminate the
message using a line with single dot. (Looked very much like
how you issue `POST` command on NNTP) This did not use
data connection at all; so theoretically, this would work over Tor.

B. Use `MLFL` (mail file) FTP command, this would look like more like uploading file; you would have to issue `PORT`/`PASV` [2] stuff to set up
data connection, and then issue `MLFL` to initiate data transfer;
and you feed the mail content to the server though that data connection,
close the data connection when you finished sending message.

Of course, these were considered "obsolete" since long time ago,
so I'd guess that unless one's FTP server allowed implementing
custom command, or one rolled their own FTP server;
support for these old stuffs (some would say "ancient" at this point)
would be really hard to come by. But I stumbled upon
these old documents several weeks ago, so I think I'd
mention it anyway; just as some food for thoughts.

Regards,
~xwindows


P.S. This post is written in mobile-friendly RFC 2646
"text/plain; format=flowed" way.

[1]
I found RFC 475 (from early 70s) summarized this the best: <https://www.rfc-editor.org/rfc/rfc475>
but it was by no means the only RFC that described/mentioned it.

[2]
A use of `PASV` with `MLFL` would be rather anachronistic,
since passive mode data connection was introduced in the 90s by RFC 1579; which was probably long after `MLFL` already fell into obscurity.
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On Fri, 26 Aug 2022 18:44:00 +0700 (+07)
xwindows <xwindows@tilde.club> wrote:

On Fri, 26 Aug 2022, Bogus User wrote:

Example, uploading email to a "magic directory" that forwards it.

Email transport over FTP used to be a thing actually;
though not exactly in the way you described. (In my understanding, mail-over-FTP was the main way of sending email to
another host in ARPANET era, before SMTP came along)

Yea, I'd heard about that too. I thought it was just a proposal.

FTP is pretty neat, but not very firewall friendly.

The library I was playing with made it pretty easy to implement your
own commands if you wanted to (it would have been easier, too) but I
felt it was better to stick with files and directories, sort of like
/dev/ might be used on the filesystem. This way any ftp client could be
used.

I'm glad I didn't waste a lot of time on it, seeing as no one was
interested in archie 2.0 anyway. :-)

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