This article is about various things that have to do with forwarding, sending and receiving as a different address

This comprehensive article describes a work around for the send as option for google. It allows addresses to be forwarded to gmail and can send as.
http://gianfaye.com/blog/gmail-send-mail-as-no-more/

This method does not work as of 2015 January (date not exact.) Please use above work around If you have an email already forwarded to your address, you may also want to be able to send out as that address so that people will always see just that address. To do this you:

1. Go to gmail settings via the gear in top right
2. Go to Accounts and Import
3. At Send Mail as, choose Add another Email address you own
4. A new windows will open, enter the email address
5. Un check Alias as this will still show your real address when sending out
6. Click next step
7. Choose Send through gmail (default)
8. Click next step
9. Choose send Verification
10. Go to your email and get the code
11. Copy code into the box and click finish