So I'm learning about SMTP and am trying to use telnet to send some mail over SMTP.
I've easilly been able to send mail to my gmail account via:
$ host gmail.com
...
gmail.com mail is handled by 5 gmail-smtp-in.l.google.com.
...
$ telnet gmail-smtp-in.l.google.com 25
Trying 74.125.142.27...
...
Connected to gmail-smtp-in.l.google.com.
...
HELO <me#test.com>
...
However, I'm having trouble sending from my gmail account. From what I understand about SMTP, I should be using SMTP to send mail from < mygmailaddress#gmail.com >
to the outgoing gmail SMTP servers, which in turn use SMTP to transfer the mail to the receivers incoming SMTP server ect.
However, I'm having difficulties. If I telnet into smtp.gmail.com via port 465 (gmail outgoing smtp mail server canonical), I'm immediately disconnected after starting with HELO <blah#blah.com>, or asked to STARTTLS. I can't find answers on how to proceed.
Any help is appreciated.
Sidenote: Currently I'm using Starbucks free Wi-Fi to access the internet. I'm actually unable to telnet directly from my computer (No route to host error). Instead, it only works if I ssh into a remote linux box on my school's network first, then telnet from there. Any idea why this is?
Thanks!
First of all, it looks like you're using the wrong port. Gmail exposes port 465 for SMTP over SSL and port 587 for SMTP with STARTTLS, as documented here. The difference between these two is that SMTP over SSL first establishes a secure SSL/TLS connection and conducts SMTP over that connection, and SMTP with STARTTLS starts with unencrypted SMTP and then switches to SSL/TLS. This is why you don't get a response to your HELO.
$ telnet smtp.gmail.com 587
Trying 74.125.25.108...
Connected to gmail-smtp-msa.l.google.com.
Escape character is '^]'.
220 mx.google.com ESMTP fr1sm24834956pbb.26 - gsmtp
HELO <me#test.com>
250 mx.google.com at your service
STARTTLS
220 2.0.0 Ready to start TLS
But even if you telnet to port 587 you still aren't going to be able to send any email by hand. In order to do anything interesting you will have to STARTTLS, and you won't be able to handle the SSL/TLS binary protocol to negotiate the encryption.
The telnet client will not negotiate a TLS session for you. You should use another tool, such as OpenSSL's s_client. The following issues the STARTTLS command for you and handles the TLS negotiation:
$ openssl s_client -starttls smtp -connect smtp.gmail.com:587 -crlf
Alternatively, you could connect directly to the SMTPS port:
$ openssl s_client -connect smtp.gmail.com:465 -crlf
Related
C:\Users\Wild Beast>openssl s_client -starttls smtp -connect smtp.gmail.com:587 CONNECTED(000001B8)
I got connected with the server and was able to login but when I use list command to read the mails. It showed the error
235 2.7.0 Accepted
list
502 5.5.1 Unrecognized command. m7-20020adfe0c7000000b002060e7bbe49sm16301005wri.45 - gsmtp
SMTP on port 587 is used for submitting emails to the outgoing mail server and has no LIST command. You may want to look into POP3 or IMAP to fetch emails from the incoming mail server of your mailbox provider. Let me know if you need help with that.
Hi am having a confusion reg SMTP ports. I have configured an application in my local machine to use gmail's smtp server by getting the details from here - https://www.siteground.com/kb/google_free_smtp_server/ and am able to trigger emails without any issues.
When I set the same application in a windows server and use the same smtp settings the emails aren't going and I keep getting errors like "unable to connect to smtp port 465". So is the port being mentioned here - 465 - is this port being used from my machine to connect to gmail's smtp server or is this port being referred to the port in the machine where gmail's smtp server is hosted?
I have tried connecting and using telnet to a gmail service for testing:
telnet gmail-smtp-in.l.google.com 25
Yet it says
Connecting to gmail-smtp-in.l.google.com failed.. Could not open connection to the host, on port 25: Connect Failed
Is this because of my firewall or am I doing something wrong?
I have tested this at work and at home and I am still unable to telnet in.
Yet, when I do an SMTP test using mxtoolbox, it seems that they can telnet in.
Is there something I am missing?
I am trying to do an SMTP test using Telnet.
Your ISP may be blocking outgoing SMTP connections to smtp (25) port as outgoing spam prevention.
Can you telnet smtp (25) port on any email host beyond your ISP network?
Can you telnet smtp.gamil.com 587?
[Port 587 is intended for client to server SMTP sessions, gmail supports it]
I am trying to send a gmail, here are the commands, using port 587:
EHLO smtp.gmail.com
STARTTLS
AUTH LOGIN
base64_encoded_username
base64_encoded_password
MAIL FROM:<me#gmail.com>
RCPT TO:<other#gmail.com>
DATA
SUBJECT: Hello!
This is the text
QUIT
The server says "Ready to start TLS" What I am doing wrong?
I could successfully send e-mail notification in Hudson using gmail as the smtp server.
But when I try to configure our own smtp server, it gives the following error when trying to send the test mail:
Failed to send out e-mail
javax.mail.MessagingException: Exception reading response;
nested exception is:
javax.net.ssl.SSLException: Unrecognized SSL message, plaintext connection?
Are there any special configurations with the e-mail notifications???
Edit:
Also does it require enforcing the security certificate and if so is there a way to achieve it???
Thanks
Please try using the following settings:
SMTP SERVER : smtp.gmail.com
use SMTP Authentication : true
use SSL : true
SMTP port : 465
I had this problem too. My solution was to make all the necessary configuration (check ssl box and stuff) and CLICK THE SAVE BUTTON before use the test mail.
i just had this issue before clicking the save button.
Changing the SMTP port from 587 to 465 also resolved this issue for me, even though I'm using an alternative SMTP service:
SMTP server: smtp.mandrill.com
Use SMTP Authentication: true
Use SSL: true
SMTP Port: 465
From what I can tell (disclaimer: I am by no means a Hudson/Jenkins expert)
the Hudson/Jenkins email plugin supports SSL encrypted SMTP communication - however this implementation requires that communications are encrypted from the get go.
When connecting on port 587, the server on the other end may expect a STARTTLS command (see this SSL vs TLS vs STARTTLS article). This command is sent using plain-text to 'upgrade' the connection to use SSL/TLS.
Hudson/Jenkins instead attempts to start negotiating SSL on port 587, which is promptly rejected, resulting in the following error:
javax.net.ssl.SSLException: Unrecognized SSL message, plaintext connection?
I also tried adding additional JAVA options "-Dmail.smtp.starttls.enable=true" (configured in /etc/default/jenkins on Unbuntu) to enable TLS:
JENKINS_JAVA_OPTIONS="-Djava.awt.headless=true -Dmail.smtp.starttls.enable=true"
Unfortunately this didn't resolve the issue for me.
After changing the port to 465, the SSL negotiation occurred correctly and the communication succeeded.
Hope that helps.