I tried to search for this, but it is hard to describe. I have gmail, and I have my work email which I'd just an alias that forwards to my gmail. I also have my own custom domain and website an another email from that... That also forward to my gmail... In gmail on my desktop iMac I can choose to send email with whatever address I want in the "from:" field. On my iPad the only option seems to be sending the email from my gmail address.
How can I fix this?