On Thu, 3 Dec 2020 at 11:39, Masataka Ohta <mohta@xxxxxxxxxxxxxxxxxxxxxxxxxx> wrote:
Christian de Larrinaga wrote:
> there are times when having telnet to test a mail server / email
> address is helpful?
Yup. In that sense, all the ASCII based protocols are
telnet servers.
This isn't true, in point of fact. FTP's control connection *is* based on TELNET, but SMTP, HTTP, and others are not.
Actually, when I teach ASCII based protocols (ftp, http, etc.)
to students, I let them use telnet clients to access servers
manually.
A conformant TELNET client implementation can (and maybe even will) send IAC commands over the link, which will confuse HTTP and SMTP, and quite possibly mildly surprise non-conformant FTP.
I'd suggest you use `nc` instead of `telnet` to avoid this risk.
Dave.
