Hi all:

I am evaluating mail servers for a small business or a volunteer-driven club or charity, mainly out of personal interest. I am in fact a newbie to mail servers: I have read a fair amount here and there, but have no practical experience at all.  In fact, I am not really a sysadmin. But I find the subject interesting nevertheless.

I wanted to learn how to implement a mail solution on premises, where no ports are exposed to the Internet, except for SSH for admin purposes, and OpenVPN for users on the road.

There is a standard ISP with a standard e-mail server. Most ISPs have now a "catch all" or "multidrop" mailbox that works reasonably well, including spam and virus detection. Alternatively, each user can have his or her own mailbox on the ISP, but will not use it directly.

E-mails should be downloaded from either that single "catch all" mailbox, or from each user's external mailbox to his/her internal mailbox.  This is what the old Microsoft Exchange with the "POP Connector" used to do.  I gather I will use a tool like fetchmail or getmail in the case of Linux.

Users will only interact with the internal mail server. If they are on the road, they need to connect with the VPN first. Yes, that is not ideal, but I want to keep complication to a minimum.

I only wanted a basic e-mail service. Nothing fancy like Groupware features. Well, an out-of-office autoresponder would be nice.

Internal e-mails will not leave the office LAN. If Internet goes down, internal e-mail still works. Hopefully including the out-of-office autoresponders.

Outgoing e-mails will be relayed to the ISP's SMTP server. This way, I do not have to worry about SPF, DNS, etc.

I have had this discussion before somewhere else:

- This setup probably does not make sense economically speaking. But I want to learn how to do it anyway.

- I will not open ANY ports to the outside world for the mail server. I will not reconfigure the firewall, etc.

I have seen a Microsoft Exchange Server with the POP Connector working in this kind of setup, and it did not need any ports open at all.

- I will not ask the ISP to do anything special with SMTP delivery.

- I will not host in the cloud.

From the description, I have the impression that iRedMail is designed to run on a server that is visible on the Internet, and that there is no alternative configuration, at least during installation.

Is there any "easy", "complete" guide about reconfiguring iRedMail to collect e-mails from the ISP, and to rely outgoing e-mails through the ISP?

If not, I would gladly collect any information, and maybe try to write such a guide myself.

If I reconfigure iRedMail in this way, should I expect many things to break? I gather that some of the GUI configuration tools or features will no longer work well.

Thanks in advance,
  rdiez