Email Setup

Trying to Setup Email . .  with my ISP email account  

Mailbox unavailable. The server response was: 5.1.0 Authentication required

What version of nopCommerce?
Does the "test" email work?
You probably should speak to your ISP support to be sure you have the correct settings.
When you say "ISP" do you really mean 'internet service provider', or do you mean the Hosting company?  (or are they one and the same?)

I´ve got similar problems

Version 4.2   . .   Is the application using the internal SMTP server?   I called my ISP. . ..  could not get it resolved.   What are people using SendGrid?

The application does not use an SMTP "Server"; it uses a SMTP Client to talk to the server.
Does the "test" email work?
What are your settings?  (post them here except dummy your domain and password)

https://drive.google.com/file/d/1-5ao2X4I4Np59VCN6TCA30MHn7jpy6AV/view?usp=sharing

@mag48
your share requires request for access.
(can you just copy paste the few fields here?)

https://drive.google.com/file/d/1-5ao2X4I4Np59VCN6TCA30MHn7jpy6AV/view?usp=sharing

Does the "test" email work?

Try changing
  Use Default Credentials: unchecked

If still a problem try
Port: 587
SSL: checked
Use Default Credentials: unchecked

Is there a more detailed error message in the System > Log?  (post it here)

The issue seems to be comcast is requiring TLS security not ssl.  What email are you using for your store?