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Validate Mail Connections with Telnet

Validate Mail Connections with Telnet

Owned by Andy Brook [Plugin People] (Unlicensed)
Last updated: Dec 30, 2014
3 min read



Validating a non-SSL POP server connection

  1. telnet host port

  2. user user

  3. pass pass

LOGIN TEST:
andy@sup-jira2:/usr/local/apps/home/log$ telnet x.y.com 110 Trying 1.2.3.4... Connected to x.y.com. Escape character is '^]'. +OK Dovecot (Ubuntu) ready. user MAILUSER +OK pass MAILPASS +OK Logged in.
LIST MESSAGES (after login):

Use LIST to list the messages, and then RETR (RETR 1) to view the given message

LIST +OK 2 messages: 1 437 2 2408 . RETR 1 +OK 437 octets Return-Path: <root@localhost> X-Original-To: andy@localhost Delivered-To: andy@localhost Received: by isoserver (Postfix, from userid 0) id C09044061F; Tue, 2 Dec 2014 13:15:11 +0000 (GMT) Subject: Test To: <andy@localhost> X-Mailer: mail (GNU Mailutils 2.99.98) Message-Id: <20141202131511.C09044061F@localhost> Date: Tue, 2 Dec 2014 13:15:11 +0000 (GMT) From: root@localhost (root) Hi there quick test
DELETE A mail
DELE 1 +OK Marked to be deleted.

 

QUITTING:

As we're using telnet, you can use CTRL + ] to close the connection, the mail server may also support quit

^] telnet> quit Connection closed.

Validating Plain SMTP

- http://www.yuki-onna.co.uk/email/smtp.html

Validating SMTP with TLS

Its also possible to do telnet style interaction with a TLS secured server (this example shows that there is a server side block on the account I am logging in as)

openssl s_client -starttls smtp -connect smtp.gmail.com:587 -crlf   CONNECTED(00000003) depth=2 C = US, O = GeoTrust Inc., CN = GeoTrust Global CA verify error:num=20:unable to get local issuer certificate verify return:0 --- Certificate chain 0 s:/C=US/ST=California/L=Mountain View/O=Google Inc/CN=smtp.gmail.com i:/C=US/O=Google Inc/CN=Google Internet Authority G2 1 s:/C=US/O=Google Inc/CN=Google Internet Authority G2 i:/C=US/O=GeoTrust Inc./CN=GeoTrust Global CA 2 s:/C=US/O=GeoTrust Inc./CN=GeoTrust Global CA i:/C=US/O=Equifax/OU=Equifax Secure Certificate Authority --- Server certificate -----BEGIN CERTIFICATE----- MIIEdjCCA16gAwIBAgIIGcMF7jeVMoAwDQYJKoZIhvcNAQEFBQAwSTELMAkGA1UE BhMCVVMxEzARBgNVBAoTCkdvb2dsZSBJbmMxJTAjBgNVBAMTHEdvb2dsZSBJbnRl cm5ldCBBdXRob3JpdHkgRzIwHhcNMTQwNzE1MDg0MDM4WhcNMTUwNDA0MTUxNTU1 WjBoMQswCQYDVQQGEwJVUzETMBEGA1UECAwKQ2FsaWZvcm5pYTEWMBQGA1UEBwwN TW91bnRhaW4gVmlldzETMBEGA1UECgwKR29vZ2xlIEluYzEXMBUGA1UEAwwOc210 cC5nbWFpbC5jb20wggEiMA0GCSqGSIb3DQEBAQUAA4IBDwAwggEKAoIBAQCu4vOr LgyNsHicxBORgO2OOfXKxEKb830NzNu6elubbf1T45GilB3fHgDQJELRydTRZilo Efv75Ag7uRQM/M1tk+1h18wDpJZem+zFmJcs30ccBN21CnCvqsIEYJMyY3kcV4vD x44bx6VvEAmJ9/kiFJ7xRUlCchu5YVOFoVkMaEax3UWb5Fti9pe8VgYdasuk53ae 8ZuIr4pFew9fraxOe/6LXEaPMSw622KSWpyK/GUbaAp07hV11c+LVgjlUDTgA+2k nDigWrdb+yLL9Hv3WNLWjEAHFWhEce5QwV3SN8JLga3Rbw2N3lq9afkQtOnkJgdM UG4xkUHGqscggMDJAgMBAAGjggFBMIIBPTAdBgNVHSUEFjAUBggrBgEFBQcDAQYI KwYBBQUHAwIwGQYDVR0RBBIwEIIOc210cC5nbWFpbC5jb20waAYIKwYBBQUHAQEE XDBaMCsGCCsGAQUFBzAChh9odHRwOi8vcGtpLmdvb2dsZS5jb20vR0lBRzIuY3J0 MCsGCCsGAQUFBzABhh9odHRwOi8vY2xpZW50czEuZ29vZ2xlLmNvbS9vY3NwMB0G A1UdDgQWBBSanZBvY+Rnj0HquJmae9AJvwiCzTAMBgNVHRMBAf8EAjAAMB8GA1Ud IwQYMBaAFErdBhYbvPZotXb1gba7Yhq6WoEvMBcGA1UdIAQQMA4wDAYKKwYBBAHW eQIFATAwBgNVHR8EKTAnMCWgI6Ahhh9odHRwOi8vcGtpLmdvb2dsZS5jb20vR0lB RzIuY3JsMA0GCSqGSIb3DQEBBQUAA4IBAQCVoGAOKZoil4sNAYvlb9uxNmWqQqyh ql0D1bewbLxs3DSVWSe2DhPjjhdMHMTcMpB+jQzAbGxVYiuNLdqLl1Xcde7EUmo1 KJUGzTO046k+11LYVOxEXLBe5s3FF+niFJby7XFgmI3yMt4blHN5tHm/7JijL1Ip vkcsynOnOwAEHehI1U12N0JEpkcoetM6MA8cGtn74EPTas4Npa+mTNo3seH8iY43 4L4hnsubXMhcQQ9IQMPtKuZYNUXklN/NS0f69Be+3HQRTOljtCxdpm/v/emHPjwg /Cwu+58fZK+flQ1PQcY24Cgt7EF0R+uqo5Il3CGuCgrd4JxJNMuGcsGS -----END CERTIFICATE----- subject=/C=US/ST=California/L=Mountain View/O=Google Inc/CN=smtp.gmail.com issuer=/C=US/O=Google Inc/CN=Google Internet Authority G2 --- No client certificate CA names sent --- SSL handshake has read 3990 bytes and written 466 bytes --- New, TLSv1/SSLv3, Cipher is ECDHE-RSA-AES128-GCM-SHA256 Server public key is 2048 bit Secure Renegotiation IS supported Compression: NONE Expansion: NONE SSL-Session: Protocol : TLSv1.2 Cipher : ECDHE-RSA-AES128-GCM-SHA256 Session-ID: EC0E1D8CA1227AE9386A2104174ADA6C7CE7AB1D62A068DC50B5FE1F5B92CBEE Session-ID-ctx: Master-Key: 4A72DA545F7AF1FB22F571F299FDDA8034691266ED34E94B7FF6DD71239B20F3CC84105C27399A2B1A61FFD5680ED231 Key-Arg : None PSK identity: None PSK identity hint: None SRP username: None TLS session ticket lifetime hint: 100800 (seconds) TLS session ticket: 0000 - d7 15 b6 8e 84 c9 af 13-f0 5d 95 16 f3 99 1e b5 .........]...... 0010 - 0d ef 79 0a ae 64 51 27-33 1e e2 d2 5b 5d 59 71 ..y..dQ'3...[]Yq 0020 - ba cb 6d 91 1e 91 fd e2-12 2e ab 54 51 87 28 7b ..m........TQ.({ 0030 - 92 19 de ac 62 d3 99 8a-86 2b b6 a5 85 89 b2 ce ....b....+...... 0040 - 10 48 9b 5d 28 d8 f1 61-4e a9 b3 0c 0d ce 03 03 .H.](..aN....... 0050 - 21 d0 fa 09 af e4 7b a7-e5 6b c2 16 c3 3a 03 ec !.....{..k...:.. 0060 - ef 8d 8e cf de 41 ba 8c-f9 57 00 a4 24 d0 34 50 .....A...W..$.4P 0070 - 00 c2 39 43 ec 3a f4 87-d3 d3 32 3c e6 8e 4e a9 ..9C.:....2<..N. 0080 - ef 7e 8a 6e a1 22 1d 8a-06 97 4f 1d cc 26 9b 85 .~.n."....O..&.. 0090 - bc 3f 2a a2 cf 36 ed 6d-10 b6 39 41 98 79 34 d8 .?*..6.m..9A.y4. 00a0 - cc 73 31 0e .s1. Start Time: 1419973684 Timeout : 300 (sec) Verify return code: 20 (unable to get local issuer certificate) --- 250 SMTPUTF8 HELO <andy@sol.thepluginpeople.com> 250 mx.google.com at your service mail from: meh@gmail.com 530-5.5.1 Authentication Required. Learn more at 530 5.5.1 http://support.google.com/mail/bin/answer.py?answer=14257 ej10sm48089217wib.1 - gsmtp

Authenticating for SMTP

Once a session has been setup as above, authentication can occur with: auth login.  What happens next is a 334 code response is sent by the server, what's wanted now is a base64 encoded value of the username (AAAAAAAAAAAAAA==), JEMHC has a Base64 Encoder in the Tools section.  After hitting enter, a further 334 code response is sent, next it wants the password, also base64 encoded.  If that worked, you're now authenticated.  If not, check Common Problems.

auth login 334 VXNlcm5hbWU6 AAAAAAAAAAAAAAAAAA== 334 UGFzc3dvcmQ6 BBBBBBBBBBBBBBBBBB== 235 2.7.0 Accepted <------------ you get this if it worked :)



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