Gmail: trying to hide the address I'm sending email from

[Simfish]

Okay, so basically I have a university email address and a gmail account. Generally I autoforward all emails to my gmail account and reply to the emails by using an option that replies to emails by my university address rather than my Gmail account. But sometimes this option results in this message occuring in the header of the previous reply:

"From: simfish@gmail.com [mailto:simfish@gmail.com] On Behalf Of XXXXX"

Does anyone know an easy way to prevent this from happening? I want a centralized Gmail address for all the emails I use, but yet I don't necessarily want people to know my gmail address. I could just create another email address but that means the inconvenience of checking (and backing up) two email accounts.

[ranger]

Google has made the Gmail Inbox centralized for some time now. That is, it does not show the "On Behalf" text and uses your domain's email server to send the email. You probably did not authenticate your school's email address from gmail using your school's outbound email server as yet.
http://gmailblog.blogspot.com/2009/07/send-mail-from-another-address-without.html

[pallidin]

You don't want some people knowing the sending email address of what they receive?
Why?

I would be very suspicious.