How to set default account in mail for specific email addresses

Thanks for the response. The setting under Composing is for mail as a programme. I cannot find a way to make that setting for each account I have. It allows me to select an account when sending mail, but this doesn't take into account who the email is going to, I still need to check in the message which account has been selected before sending the email. I would like to default the email address when sending email to particular addresses in the same way that I can set rules to have emails from specific email addresses to be stored into a specified message folder.

Yes, but I cannot see where to assign the choice to a specific account. So say three accounts a@gmail.com, b@gmail.com and c@gmail.co,. I use each one for a specific purpose and only want b@gmail.com to be used when sending email to specific people with email addresses ending say in @xyccompany, and a@gmail, I want to use only for sending email for personal use. Yes what you show allows me to select one of those accounts as the default email address, but it gets used irrespective of who I am sending email to. Compare it to the "rules" where if email comes from @xycompany, I can have that email automatically stored in a folder called 'xycompany'. I am looking for the corollary of that, where I assign a particular account when sending to a specific email address.

Yes that is how it is set, but I need it to look at the email address I am sending to and select the correct account to reply back with. So I am constantly looking at emails to all my accounts, so the last one is often NOT the account I want the next email to be sent from. As per the "rules" style, I would like Mail to look at the email address I am sending to and automatically select the appropriate account to send from.

Yes I agree . Maybe someone from Apple will see this and look at adding this feature in. It would be a handy feature, in the same way as the 'Rules' is. I thought I would pose this poser in case there was some hidden aspect of Mail that I had not found. Thanks for trying.