Reply from same address as mail was sent to in Mail.app
Apple Mail can only send replies from mail enabled accounts that you have set up in your system. I.e., you may have iCloud account set up in your system, but if you have mail option unchecked in System Preferences -> Internet Accounts -> iCloud, you won't be able to send any mail (including replies) from that iCloud account.
One possible workaround is to use 'Reply To' field which you can enable by pressing Alt+Command+R or from Main Menu -> View -> Reply-To Address Field. This will enable your recipients press reply button and send their reply to the address which you will enter into mentioned field.
Hope this helps.