I'm using a catch-all domain for all my e-mail communication. I'm also using iOS and currently have to log in to my web panel via Firefox/Safari when I want to write someone with a custom "From" address. It's really unpleasant.<p>Is there software for iOS which allows me to set the the "From" field on the fly without complicated account/identity management? Thunderbird would be something which has this, but it's desktop only.<p>The native Mail app only lets me allow to change the sender account but there's no way to modify the From address.
If you’re willing to move to FastMail, FastMail’s native iOS app has this. You can rewrite the from address to use any username, any real name string, and/or any subdomain within your domain. There’s no additional setup, you’re just able to edit the from address in the compose screen.
I’m fairly certain you can create an account in iOS mail with whatever address you want, leave the incoming credentials blank, and choose an existing SMTP account for outgoing. At least that’s how I used to do it.