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--- email:test_smtp [2016/07/05 17:47] – [Obtain the DNS MX record for a domain] peter
+++ email:test_smtp [2019/11/27 22:15] (current) – removed peter
@@ Line 1: / Line 1: @@
-====== Email - Test SMTP ======
-The commands used here are covered in section 4.1 of RFC 2821 [http://www.ietf.org/rfc/rfc2821.txt].
-===== Obtain the DNS MX record for a domain =====
-Issue the following command:
-**Linux:**
-<code bash>
-nslookup -type=mx sharewiz.net
-Non-authoritative answer:
-sharewiz.net      mail exchanger = 10 mail.sharewiz.net.
-Authoritative answers can be found from:
-mail.sharewiz.net	internet address = 5.42.134.35
-</code>
-**Windows:**
-<code bash>
-nslookup -type=mx sharewiz.net
-Non-authoritative answer:
-sharewiz.net      MX preference = 10, mail exchanger = mail.sharewiz.net.
-</code>
-===== Get the DNS PTR for the IP =====
-This requires to know what IP address.
-With the IP address run the following command, where A.B.C.D is the IP address.
-**Linux:**
-<code bash>
-nslookup -type=ptr A.B.C.D
-Non-authoritative answer:  D.C.B.A.in-addr.arpa  name = server.example.com
-</code>
-**Windows:**
-<code bash>
-nslookup -type=ptr A.B.C.D
-Non-authoritative answer:  D.C.B.A.in-addr.arpa  name = server.example.com
-</code>
-So now that we have the MX record for example.com and the PTR for the IP we are going to use, it is time to login to the SMTP server.
-===== Connect to server =====
-For non-secure SMTP, you can use
-<code bash>
-telnet example.com 25
-</code>
-For secure SMTP, you can use one of following:
-<code bash>
-openssl s_client -starttls smtp -connect example.com:25
-openssl s_client -starttls smtp -connect example.com:465
-openssl s_client -starttls smtp -connect example.com:587
-</code>
-As soon as you connect to the server, run:
-<code bash>
-ehlo example.com
-</code>
-You will get output like below as reply:
-<code>
--test.rtcamp.com
--PIPELINING
--SIZE 10240000
--VRFY
--ETRN
--STARTTLS
--AUTH PLAIN LOGIN
--ENHANCEDSTATUSCODES
--8BITMIME
-DSN
-</code>
-If you do not see line like 250-AUTH ... line, then your server may not support authentication.  Most likely you will see this when trying with telnet or openssl without startls.
-===== Authentication =====
-For admin@example.com and password, generate base64 encoded string like below:
-<code bash>
-echo -ne '\0admin@example.com\0password' | base64
-</code>
-Please note use of **\0** before username and password.  It must be used as it is.  Also, use single-quotes to avoid escaping special characters in your password.
-It will output a string like below:
-<code>
-AGFkbWluQGV4YW1wbGUuY29tAHBhc3N3b3Jk
-</code>
-Use above string with AUTH command:
-<code bash>
-AUTH PLAIN AGFkbWluQGV4YW1wbGUuY29tAHBhc3N3b3Jk
-</code>
-===== SMTP Commands to send test email =====
-Type/paste following commands 1-by-1.  They are interactive and needs input.
-<code bash>
-ehlo example.com
-mail from: admin@example.com
-rcpt to: admin@other.com
-data
-quit
-</code>
-For more SMTP Tests, check http://www.stat.ufl.edu/system/mailtesting.shtml.
-===== Open-Relay Test =====
-Worst thing that could happen to your SMTP server is – it becomes open-relay (accidentally).  An open-relay allows anybody to connect and send email using your server.  It can lead to your server being blacklisted.  I am not sure if it can result in legal hassles!
-There are many tools available online which can check if your smtp server is acting as open relay.
-===== swaks utility =====
-This is a small package which can make it easy to test your smtp server.
-<code bash>
-apt-get install swaks
-</code>
-Example usage:
-<code bash>
-swaks --server example.com --to admin@example.com
-</code>
-Please note that SpamAssassin marks, swaks generated email as spam.