For those reading this and wondering how to manage other domain eMails, it is very easy in gmail.
First, register your domain, and get all mail redirected to a gmail account.
Then, go into gmail, choose settings, Accounts and Import.
There you will see "Add another eMail address you own", use this to add your new domain.
After gmail has confirmed you own it by sending a mail to which you click to confirm, you will be able to send mail from gmail with your own domain.
You can choose any address to be your default for new emails. The normal way gmail is set up it will respond to a mail with the domain that receives is. So, if you receive a mail addressed to me@posh.com, it will send a reply from posh.com without further intervention, you can change this on a case by case basis if you want to.
Repeat as many times as you have domains.
You may find it useful to use gmail filters to tag incoming mail with a domain and put it into its own folder.