I would like to understand how exchange email travels to and from internet in the environment where they have front end/back end exchange servers and environment where they have just one exchange server.
like what 's the step by step route of an email from inside LAN to external user? ex:
1-user send email to a destination user such as email@example.com
2-internal DNS will use iterative request to com dns then to dot (.) DNS, all the waw down until iit finds externaldomain.com on the internet and will map its name to the registered public IP address (18.104.22.168)
3-the email is transmitted to externaldomain.com public IP address 22.214.171.124
4-at this point I don't know if the 126.96.36.199 is the external interface of the firewall of the other company or what type of device it is..
5- if so how does the device with 188.8.131.52 finds the A record and MX record of the DNS of the other company since the A record and MX record in the DNS uses private IP addresses?
6-what's the step by step route of an email from outside to the inside exchange server?
If you can describe both scenarios where front/back end is used and when it is not used that will help.
These steps are just examples so that yopu will know what I am trying to understand.
Thanks a lot.