I'm trying to send email using telnet in cmd. I have connection with telnet now. Btw I'm using a disposable email provider.
C:\Users\Student>telnet mail.dispostable.com 25
then it brought me here:
220 dispostable.com ESMTP
then I type the following command:
ehlo mail.dispostable.com
and I got:
250-Hi
250 SIZE 50000
I have successfully entered the "mail from:" command and received the 250 message successfully (means I'm set) but suddenly I failed on the "rcpt to:"
mail from: caaquino@dispostable.com
250 OK
rcpt to: cedr******@gmail.com
550 User Unknown
Can someone please enlighten me if I'm doing the right thing on choosing a temporary email provider as the sender account of this email and using Gmail as the receiver/victim.
I've been trying various email accounts for the recepients and always receive the 550 user unknown error.
Best Answer
As far as I can see,
dispostable.com
does not offer outgoing mail relaying. They have mail servers that accept incoming mail to@dispostable.com
addresses, but haven't configured them to allow sending mail to any address from@dispostable.com
.In other words, the error message means, "You cannot relay mail through me to
@gmail.com
."This means that you would have to connect either directly to the recipient's incoming-mail servers, or to an open relay server. (I honestly doubt you could find many open relays on today's spam-filled Internet.) For example,
@gmail.com
's incoming mail is handled by:However, if you do this, Gmail will likely reject your message as spam, because they will find a SPF record at
dispostable.com
saying that no servers should send mail claiming to from that domain:Most "real" mail providers do give users access through mail relay servers. In the past, you could use them pretty much the same way, by connecting to port :25 and sending the message.
However, nowadays "incoming" and "outgoing (relay)" services are generally kept separate; the latter runs onĀ portĀ :587 and almost always requires authentication (password login). This is possible to do by hand, but isn't too easy.
Most mail relay servers also only allow logins over TLS (SSL) encrypted connections, so you'd need
openssl s_client
orgnutls-cli
instead of plain oldtelnet
.And, also, this is the correct syntax:
Note the
< >
s around the address, and no spaces afterFROM:
. Many servers accept variations, but some reject everything except this syntax.