Apple Mail Cannot Send from iCloud

Hi,

So, this has actually been going on since my initial Mini setup, but for unimportant reasons, I am just addressing now.

I have an iCloud email alias that I have been using since the option was available. I use that alias for work. I have the email set to be the automatic 'reply to' default. I also have a rule to send all those emails to its own folder and a Smart Folder for emails for that day. This is to illustrate how important it is to be sure that email default is working.

What's been happening is that it has been defaulting to my Apple ID email as the 'reply to' which is absolutely unacceptable, and because I am in the habit of using the setting, emails have been sent with this address and as a result, I have been sent emails to this address. For reasons that are not important, this email is only used for my Apple ID, I never give out this email.

Here is what I am seeing: both my main and alias iCloud addresses are missing. The check email is the Apple ID email. It seems as though I am getting the emails to these addresses, but cannot SEND from these addresses.

EDIT: I added this so you could see in the Mail settings that the emails don't even show up there. Only shows my Apple ID email, which actually has its own Account setup.

I have signed out, signed back in, updated everything, re-started, etc. and it does come back, but I cannot get it to stay, it repeatedly disappears.

Thank you!

Lisa in Atlanta