Comment by Twisol
13 days ago
The difference between "telnet" the program and "telnet" the protocol is especially important in this discussion, I think.
A more "proper" tool for that is netcat -- I doubt SMTP supports the Telnet option negotiations subsystem. (I also doubt SMTP servers can interpret the full suite of Network Virtual Terminal (NVT) commands that the Telnet protocol supports.) There's clearly enough similarity between the two protocols that if you're just using it to transfer plaintext it will probably work out fine, but they are distinct protocols.
When I find nc on a customer's Windows box, I'll be sure to use it 8)
Oh and I did mention swaks. nc comes from a time when SSL was a newish thing. swaks can do TLS with nobs on.