How to send email using simple SMTP commands via Gmail

Question

For educational purposes  I need to send an email through an SMTP server  using SMTP s fundamental and simple rules    I was able to do that using smtp4dev  I telnet localhost 25 and and commands are     I want to do the same thing  using Gmail SMTP server  However  it requires authentication and TLS  I can t figure out how to do that for Gmail  Here s a screenshot of telnet smtp gmail com 587     I searched and found many links including Wikipedia s article about STARTTLS command  But I m not able to use TLS and authenticate to Gmail s SMTP server using command line  or sending commands myself in programming languages   Can anyone help

User · Answer

As no one has mentioned - I would suggest to use great tool for such purpose - swaks

# yum info swaks
Installed Packages
Name        : swaks
Arch        : noarch
Version     : 20130209.0
Release     : 3.el6
Size        : 287 k
Repo        : installed
From repo   : epel
Summary     : Command-line SMTP transaction tester
URL         : http://www.jetmore.org/john/code/swaks
License     : GPLv2+
Description : Swiss Army Knife SMTP: A command line SMTP tester. Swaks can test
            : various aspects of your SMTP server, including TLS and AUTH.

It has a lot of options and can do almost everything you want.

GMAIL: STARTTLS, SSLv3 (and yes, in 2016 gmail still support sslv3)

$ echo "Hello world" | swaks -4 --server smtp.gmail.com:587 --from [email protected] --to [email protected] -tls --tls-protocol sslv3 --auth PLAIN --auth-user [email protected] --auth-password 7654321 --h-Subject "Test message" --body -
=== Trying smtp.gmail.com:587...
=== Connected to smtp.gmail.com.
<-  220 smtp.gmail.com ESMTP h8sm76342lbd.48 - gsmtp
 -> EHLO www.example.net
<-  250-smtp.gmail.com at your service, [193.243.156.26]
<-  250-SIZE 35882577
<-  250-8BITMIME
<-  250-STARTTLS
<-  250-ENHANCEDSTATUSCODES
<-  250-PIPELINING
<-  250-CHUNKING
<-  250 SMTPUTF8
 -> STARTTLS
<-  220 2.0.0 Ready to start TLS
=== TLS started with cipher SSLv3:RC4-SHA:128
=== TLS no local certificate set
=== TLS peer DN="/C=US/ST=California/L=Mountain View/O=Google Inc/CN=smtp.gmail.com"
 ~> EHLO www.example.net
<~  250-smtp.gmail.com at your service, [193.243.156.26]
<~  250-SIZE 35882577
<~  250-8BITMIME
<~  250-AUTH LOGIN PLAIN XOAUTH2 PLAIN-CLIENTTOKEN OAUTHBEARER XOAUTH
<~  250-ENHANCEDSTATUSCODES
<~  250-PIPELINING
<~  250-CHUNKING
<~  250 SMTPUTF8
 ~> AUTH PLAIN AGFhQxsZXguaGhMGdATGV4X2hoYtYWlsLmNvbQBS9TU1MjQ=
<~  235 2.7.0 Accepted
 ~> MAIL FROM:<[email protected]>
<~  250 2.1.0 OK h8sm76342lbd.48 - gsmtp
 ~> RCPT TO:<[email protected]>
<~  250 2.1.5 OK h8sm76342lbd.48 - gsmtp
 ~> DATA
<~  354  Go ahead h8sm76342lbd.48 - gsmtp
 ~> Date: Wed, 17 Feb 2016 09:49:03 +0000
 ~> To: [email protected]
 ~> From: [email protected]
 ~> Subject: Test message
 ~> X-Mailer: swaks v20130209.0 jetmore.org/john/code/swaks/
 ~>
 ~> Hello world
 ~>
 ~>
 ~> .
<~  250 2.0.0 OK 1455702544 h8sm76342lbd.48 - gsmtp
 ~> QUIT
<~  221 2.0.0 closing connection h8sm76342lbd.48 - gsmtp
=== Connection closed with remote host.

YAHOO: TLS aka SMTPS, tlsv1.2

$ echo "Hello world" | swaks -4 --server smtp.mail.yahoo.com:465 --from [email protected] --to [email protected] --tlsc --tls-protocol tlsv1_2 --auth PLAIN --auth-user [email protected] --auth-password 7654321 --h-Subject "Test message" --body -
=== Trying smtp.mail.yahoo.com:465...
=== Connected to smtp.mail.yahoo.com.
=== TLS started with cipher TLSv1.2:ECDHE-RSA-AES128-GCM-SHA256:128
=== TLS no local certificate set
=== TLS peer DN="/C=US/ST=California/L=Sunnyvale/O=Yahoo Inc./OU=Information Technology/CN=smtp.mail.yahoo.com"
<~  220 smtp.mail.yahoo.com ESMTP ready
 ~> EHLO www.example.net
<~  250-smtp.mail.yahoo.com
<~  250-PIPELINING
<~  250-SIZE 41697280
<~  250-8 BITMIME
<~  250 AUTH PLAIN LOGIN XOAUTH2 XYMCOOKIE
 ~> AUTH PLAIN AGFhQxsZXguaGhMGdATGV4X2hoYtYWlsLmNvbQBS9TU1MjQ=
<~  235 2.0.0 OK
 ~> MAIL FROM:<[email protected]>
<~  250 OK , completed
 ~> RCPT TO:<[email protected]>
<~  250 OK , completed
 ~> DATA
<~  354 Start Mail. End with CRLF.CRLF
 ~> Date: Wed, 17 Feb 2016 10:08:28 +0000
 ~> To: [email protected]
 ~> From: [email protected]
 ~> Subject: Test message
 ~> X-Mailer: swaks v20130209.0 jetmore.org/john/code/swaks/
 ~>
 ~> Hello world
 ~>
 ~>
 ~> .
<~  250 OK , completed
 ~> QUIT
<~  221 Service Closing transmission
=== Connection closed with remote host.

I have been using swaks to send email notifications from nagios via gmail for last 5 years without any problem.

User · Answer

Based on the existing answers  here s a step-by-step guide to sending automated e-mails over SMTP  using a GMail account  from the command line  without disclosing the password   Requirements  First  install the following software packages    Expect OpenSSL Core Utils  base64    These instructions assume a Linux operating system  but should be reasonably easy to port to Windows  via Cygwin or native equivalents   or other operating system   Authentication  Save the following shell script as authentication sh      bin bash    Asks for a username and password  then spits out the encoded value for   use with authentication against SMTP servers   echo -n  Email  shown     read email echo -n  Password  hidden     read -s password echo  TEXT   0 email 0 password   echo -ne  TEXT   base64   Make it executable and run it as follows   chmod  x authentication sh   authentication sh   When prompted  provide your e-mail address and password  This will look something like   Email  shown   bob gmail com Password  hidden    AGJvYkBnbWFpbC5jb20AYm9iaXN0aGViZXN0cGVyc29uZXZlcg     Copy the last line  AGJ        as this will be used for authentication   Notification  Save the following expect script as notify sh  note the first line refers to the expect program       usr bin expect  set address   lindex  argv 0   set subject   lindex  argv 1   set ts date   lindex  argv 2   set ts time   lindex  argv 3    set timeout 10 spawn openssl s client -connect smtp gmail com 465 -crlf -ign eof   expect  220      send  EHLO localhost n     expect  250        send  AUTH PLAIN YOUR AUTHENTICATION CODE n       expect  235          send  MAIL FROM   lt YOUR EMAIL ADDRESS gt  n         expect  250            send  RCPT TO   lt  address gt  n           expect  250              send  DATA n             expect  354                send  Subject   subject n n              send  Email sent on  ts date at  ts time  n              send   n  n               expect  250                    send  quit n                                                            Make the following changes    Paste over YOUR AUTHENTICATION CODE with the authentication code generated by the authentication script  Change YOUR EMAIL ADDRESS with the e-mail address used to generate the authentication code  Save the file    For example  note the angle brackets are retained for the e-mail address    send  AUTH PLAIN AGJvYkBnbWFpbC5jb20AYm9iaXN0aGViZXN0cGVyc29uZXZlcg   n  send  MAIL FROM   lt bob gmail com gt  n    Lastly  make the notify script executable as follows   chmod  x notify sh   Send E-mail  Send an e-mail from the command line as follows     notify sh recipient domain com  Command Line   March 14   15 52

User · Answer

Unfortunately as I am forced to use a windows server I have been unable to get openssl working in the way the above answer suggests    However I was able to get a similar program called stunnel  which can be downloaded from here  to work  I got the idea from www tech-and-dev com but I had to change the instructions slightly  Here is what I did    Install telnet client on the windows box  Download stunnel   I downloaded and installed a file called stunnel-4 56-installer exe   Once installed you then needed to locate the stunnel conf config file  which in my case I installed to C  Program Files  x86  stunnel Then  you need to open this file in a text viewer such as notepad  Look for  gmail-smtp  and remove the semicolon on the client line below  in the stunnel conf file  every line that starts with a semicolon is a comment   You should end up with something like    gmail-smtp  client   yes accept   127 0 0 1 25 connect   smtp gmail com 465   Once you have done this save the stunnel conf file and reload the config  to do this use the stunnel GUI program  and click on configuration  Reload     Now you should be ready to send email in the windows telnet client  Go to Start  run  cmd   Once cmd is open type in the following and press Enter    telnet localhost 25   You should then see something similar to the following   220 mx google com ESMTP f14sm1400408wbe 2   You will then need to reply by typing the following and pressing enter    helo google   This should give you the following response   250 mx google com at your service   If you get this you then need to type the following and press enter    ehlo google   This should then give you the following response   250-mx google com at your service   212 28 228 49  250-SIZE 35651584 250-8BITMIME 250-AUTH LOGIN PLAIN XOAUTH 250 ENHANCEDSTATUSCODES   Now you should be ready to authenticate with your Gmail details  To do this type the following and press enter    AUTH LOGIN   This should then give you the following response   334 VXNlcm5hbWU6   This means that we are ready to authenticate by using our gmail address and password   However since this is an encrypted session  we re going to have to send the email and password encoded in base64  To encode your email and password  you can use a converter program or an online website to encode it  for example base64 or search on google for    base64 online encoding      I reccomend you do not touch the cmd telnet session again until you have done this    For example test gmail com would become dGVzdEBnbWFpbC5jb20  and password would become cGFzc3dvcmQ   Once you have done this copy and paste your converted base64 username into the cmd telnet session and press enter  This should give you following response   334 UGFzc3dvcmQ6   Now copy and paste your converted base64 password into the cmd telnet session and press enter  This should give you following response if both login credentials are correct   235 2 7 0 Accepted   You should now enter the sender email  should be the same as the username  in the following  format and press enter    MAIL FROM  lt test gmail com gt    This should give you the following response   250 2 1 0 OK x23sm1104292weq 10   You can now enter the recipient email address in a similar format and press enter    RCPT TO  lt recipient gmail com gt    This should give you the following response   250 2 1 5 OK x23sm1104292weq 10   Now you will need to type the following and press enter    DATA   Which should give you the following response   354  Go ahead x23sm1104292weq 10   Now we can start to compose the message  To do this enter your message in the following format  Tip  do this in notepad and copy the entire message into the cmd telnet session    From  Test  lt test gmail com gt  To  Me  lt recipient gmail com gt  Subject  Testing email from telnet This is the body  Adding more lines to the body message    When you have finished the email enter a dot       This should give you the following response   250 2 0 0 OK 1288307376 x23sm1104292weq 10   And now you need to end your session by typing the following and pressing enter   QUIT   This should give you the following response   221 2 0 0 closing connection x23sm1104292weq 10 Connection to host lost    And your email should now be in the recipient   s mailbox

User · Answer

to send over gmail  you need to use an encrypted connection  this is not possible with telnet alone  but you can use tools like openssl  either connect using the starttls option in openssl to convert the plain connection to encrypted     openssl s client -starttls smtp -connect smtp gmail com 587 -crlf -ign eof  or connect to a ssl sockect directly     openssl s client -connect smtp gmail com 465 -crlf -ign eof  EHLO localhost  after that  authenticate to the server using the base64 encoded username password  AUTH PLAIN AG15ZW1haWxAZ21haWwuY29tAG15cGFzc3dvcmQ   to get this from the commandline   echo -ne   00user gmail com 00password    base64 AHVzZXJAZ21haWwuY29tAHBhc3N3b3Jk   then continue with  mail from   like in your example  example session   openssl s client -connect smtp gmail com 465 -crlf -ign eof      lots of openssl output      220 mx google com ESMTP m46sm11546481eeh 9 EHLO localhost 250-mx google com at your service   1 2 3 4  250-SIZE 35882577 250-8BITMIME 250-AUTH LOGIN PLAIN XOAUTH 250 ENHANCEDSTATUSCODES AUTH PLAIN AG5pY2UudHJ5QGdtYWlsLmNvbQBub2l0c25vdG15cGFzc3dvcmQ  235 2 7 0 Accepted MAIL FROM   lt gryphius-demo gmail com gt  250 2 1 0 OK m46sm11546481eeh 9 rcpt to   lt somepoorguy example com gt  250 2 1 5 OK m46sm11546481eeh 9 DATA 354  Go ahead m46sm11546481eeh 9 Subject  it works  yay    250 2 0 0 OK 1339757532 m46sm11546481eeh 9 quit 221 2 0 0 closing connection m46sm11546481eeh 9 read errno 0

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