I have an ubuntu machine setup as a gateway server for 3 PCs. I would like to have it handle our e-mails though as well.
What I would like to do is have the ubuntu box to download all the mail for 4 different mail accounts (from the same domain, say example.com) so
user1.example.com, user2.example.com, user3.example.com & user4.example.com (these exist on my website www.example.com)
whenever a new mail arrives, or a small intervals say 10 minutes and store it locally (on the server). Then when I open my e-mail client on one of the other PCs retrieve mail from ubuntu box and not from pop.example.com for, say, user2.example.com
After that I would also like to be able to use the server for sending mail from the 3 PCs without waiting for large attachements to be uploaded. So say user2 sends a mail with a 5MB attachments, should see the message instantly leave and then the message should be send asap from the ubuntu server.
Note that I am looking for a fullblown mailserver implementation and that chances are that I will not have to make any changes any time soon on the size of the implementation.
What programs should I use and how should I configure them? I want my outgoing e-mails to be [email protected] (do they have to go through my websites mail server to be appended the example.com, do I have to change anything in the MX records on my website (note that the ubuntu server does not have a good uptime and thus could not use it as a primary mail server).
Thanks and sorry for the length of the message, just trying to be clear.