In Gmail for iOS (both the app and the site in Safari), you can. Picking any address you've previously set up for sending in Gmail is easy. (You cannot add new email addresses to the list right on the device, though.)
Send Email From an Alternate Address in Gmail for iPhone and iPad
To send a message using an email address other than your Gmail address in the From: line from Gmail on iPhone and iPad:
- Make sure the address you want to use is set up for sending in your Gmail account. (You can do this in Gmail's desktop web version.)
- Start a new message in Gmail using the Gmail app for iOS or Gmail in iOS Safari.
- Tap Cc/Bcc, From:.
- Now tap From.
- Select the email address and name you would like to appear in the From: line of the message you are composing.
- Continue composing the email and eventually tap Send.
(Updated May 2013)