I used to do this, until I had to reply to an automated email for some customer support system. It rejected all my replies because the From: didn't match.
Yeah you can, you can default it to send from the address the email you're replying to was sent to too.
It's the only thing I missed when I switched to Fastmail. (Which has since added it too, but not before I left in favour of my own SES-based solution.)
Sorry, it's many years since I've used gmail, don't have an account to check and describe exactly. I suppose I should've said 'you certainly used to be able to', I don't know for sure you still can.. would be dumb to remove that though.
Iirc there was a section of settings called 'sending & receiving', and there was a drop-down to select 'reply from same address' or similar.
That option is only for fixed addresses, not catchall addresses.
I.e. if your main email address is ojford@ojford.com but you're also preconfigured e.g. foobar@ojford.com you could set that option to have Gmail use either ojford@ojford.com or foobar@ojford.com as your return address, depending on the originating email's TO address. However, if you _also_ have a catchall address and somebody sends to newservice@ojford.com, even with the setting set your return address would be ojford@ojford.com.
Hm.. ok, I thought it worked but perhaps not - it has been a long time. I use my own client now, so obviously it behaves exactly as I want :) (which is as you describe).
Current Thunderbird does enable the From address to be edited in the Compose window, and can fill in that field from the TO address of the message being replied to. Previous Thunderbird versions needed an Addon called Virtual Identities to do this.
