I use my gmail account to send email from my school address on my computer. I would like to do the same from my phone but I don't see how I can do it, or if it is even possible.
It's not possible I'm afraid, well not through the actual gmail application on the phone. I also use several different email accounts from gmail and it's something that is a missing for me also.
I would hope so as I can see the filters I have set up within the gmail application as it pulls all the emails from my different accounts but I just can't reply via the same address. Now it's not a major problem as my main email address is the one set up but it would be handy to be able to reply to others from the address that it was sent to. I normally just read it then reply once I am back to my pc. It's a minor pain but yes something I would like.
I use my gmail address for reply to, but my wife uses her yahoo address for a reply to. Maybe this would work for you: From Gmail:
I am sending from my Hotmail account, using Gmail. (Android 2.3.4) Just add another account under "Accounts & sync".