"Unable to Verify Account Name or Password" error message

I am using Apple mail on an iMac with Mojave, with Comcast as the provider and POP3 for incoming servers. Comcast changed its rules and now it requires dedicated outgoing servers for each email address. I have 4 email addresses which until now shared outgoing servers. I was told by Comcast that in order for my email to work, I have to add new, dedicated outgoing servers for each incoming server (email address) using Apple Mail Preferences.

I followed the setup process in Apple Mail, using the same user name and password for incoming and outgoing mail servers. I attached a screen capture. Unfortunately regardless how many times I went through the process to add a new outgoing server for one of my email addresses, the info I

entered under Mail/Preferences/Accounts/Server Settings (for the

"account" in question)/Outgoing Mail Server/Edit SMTP Server List, is NOT retained. There is NO Save option. When I want to back out, a Save button appears. Clicking on it, brings up "Verifying server settings", which then displays "Unable to verify account name or password".

After doing the above, the Server Settings/Outgoing Mail Server for the email address in question, shows "NONE" and this email address is no longer accessible...  I repeated the

process of trying to add a new dedicated outgoing server, but without

any success.

I am stuck with Comcast and Apple pointing to each other, while my main email can no longer send mail. So I am authenticating with one email address and sending from another one as I have no choice and Comcast is telling me that "Your client is set to authenticate as one name but send as another- basically authenticate as userA@comcast.net and send as UserB@comcast.net. We are seeing bad guys use this to send spam/phishing emails, so we are moving to prevent this in the future. I have exempted you for now, but this needs to be rectified in your settings." However, they are not telling me how to rectify the settings, as that's an Apple "issue". Apple advisors have no clue about this whole topic and are stating that this is a Comcast issue.

I am not a technical user and I have no idea how to solve this problem. Any help would be much appreciated.