I have the following setup(hardware): One root server, out in the internet with a Domain example.com pointing to this server. An intranet, inside a company, containing several PCs.

Currently the mail traffic is handled by the root server and clients (Outlook) from within the intranet can send mails via the root server. The mail retrieval is only allowed for two employees within the company, they dispatch the mails to the remaining employees via the filesystem.

So far so good. My custromer now assiged me the task to have an individual email address for each employee inside the company. This would lead to employeeA@example.com, employeeB@example.com, etc. Nevertheless, there is still the requirement, that these addresses are invisible from outside the company. My customer wants to have one single email address, e.g. mail@example.com from which the two dispatcher employees retrieve the mails. When other employees send mails, the mail should be sent from mail@example.com as well as replys to this mail should be received by mail@example.com. Inside the company however it should be possible that one employee with the address employeeA@example.com gets a mail forwarded from mail@example.com or employeeB@example.com should be able to send an email to employeeA@example.com

I hope the description of the problem is somehow intelligible. Does anyone know a good approach for this kind of problem?

1 Answer 1


This would probably be more easily implemented with separate servers, a simple mail gateway which accepts mail for mail@example.com and is listed as the public MX server. It would then forward all messages into your intranet mail server, where all the employee mail is hosted. The internal server would implement the internal forwarding, and allow mail from employee A and B to be forwarded by the public mail gateway.

To block/allow mail to external domains, it really depends what software you're using to implement it. In postfix it's quite straightforward.

  • I am free with the choice of the software to use, would you recommend postfix? Can you provide some links?
    – Coxer
    Apr 14, 2014 at 21:06
  • You can use many different types of mailer software, postfix is my personal choice, but it's by no means the only one to be able to do this.. for postfix, this is a start: postfix.org/STANDARD_CONFIGURATION_README.html#firewall
    – NickW
    Apr 25, 2014 at 8:21

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