Testing external emails are received without forcing authentication

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To perform this test use any public machine such as AWS VM or other ISP connection. This would ensure that mail server treats the test machine as a random external machine and not a trusted machine. From such machine use following steps:

1. telnet <mail-server-public-ip> 25
2. Enter "EHLO testing" after mail server greeting
3. Then enter following lines into telnet prompt for sending email one line at a time. After each line mail server should respond that things are fine.

   MAIL FROM: saurabh@example.com
   RCPT TO: <user>@<our-domain.com>
   DATA
   Subject: This is a test email from outside domains to our company domain
   #Intentional blank line.  Thus after typing Subject: line press enter twice
   This is test email
   
   .     #A single dot on line to terminate mail
   QUIT  #To close telnet session / TCP connection

   A message that 'message has been accepted for delivery' should be received.

If this does not works then mail server being tested will not receive emails from external domains. Note that this step just checks firewall configuration, email server configuration to receive emails for given domain, etc. For proper working of emails DNS MX, A records should also be set properly which we have not verified here.

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