What? No, of course not. If you have your own server, and you set it up correctly, each user should only be able to see their own email. BUT, the server administrator CAN see everything locally (he should, so he can debug any problem). But that server administrator can only see HIS server's emails (and any outgoing email) but cannot see any email from any other server. I hope I'm clear...

Some people with enough rights will be able to do this on the servers. If you don't want to have this, you can encrypt your email: "E-mail privacy, without some security precautions, can be compromised because: e-mail messages are generally not encrypted; e-mail messages have to go through intermediate computers before reaching their destination, meaning it is relatively easy for others to intercept and read messages; many Internet Service Providers (ISP) store copies of your e-mail messages on their mail servers before they are delivered. The backups of these can remain up to several months on their server, even if you delete them in your mailbox; the Received: headers and other information in the e-mail can often identify the sender, preventing anonymous communication. There are cryptography applications that can serve as a remedy to one or more of the above. For example, Virtual Private Networks or the Tor anonymity network can be used to encrypt traffic from the user machine to a safer network while GPG, PGP or S/MIME can be used for end-to-end message encryption, and SMTP STARTTLS or SMTP over Transport Layer Security/Secure Sockets Layer can be used to encrypt communications for a single mail hop between the SMTP client and the SMTP server. Additionally, many mail user agents do not protect logins and passwords, making them easy to intercept by an attacker. Encrypted authentication schemes such as SASL prevent this. Finally, attached files share many of the same hazards as those found in peer-to-peer filesharing. Attached files may contain trojans or viruses." Source and further information: http://en.wikipedia.org/wiki/Email#Privacy_concerns

I think so...I'm not sure but I hate the way that sounds too.