How to build a world-class email server?

I have some ideas about the next email services. So I would like to build a world-class email server.

(The kind of mail server that could compete with Gmail and Hotmail in a near futur - say, two years.)

How should I start ? I mean, what language and what kind of repository ? Ruby, Java ? Oracle, MySQL ?

Any open source suggestion (I already know JAMES) 开发者_运维知识库?

Thank you.

Yave you looked at the source for the most widely used email server to get an idea of what to use and what their strengths and weaknesses are?

Some MTAs to look at are Postfix, QMail, Exim and Sendmail. Here is a good comparison of those: http://shearer.org/MTA_Comparison

I recently developed an email hosting solution, http://fijisoftware.com/ based on top of Postfix and must say it is a very robust server and can handle hundreds of thousands of users per server. I chose it because it's used by the largest open source email solution, http://www.zimbra.com/. I'd suggest studing the architecture of that server.

Usually mail servers are part MTA to handle SMTP and the other part that handles POP and IMAP are usually separate programs integrated, such as Courier, Dovecot etc. So you'd have to compare and study those as well.