Add a notification to let the user know the Mail Sending is not configured when an email needs to be sent

There are cases when users need for example to share a page or receive notifications on email, but the Mail Sending is not configured, so the emails cannot be sent.

When sharing a page, the error message is displayed on the top of the page as 'email server error'. An error is displayed also in console, but users do not have usually access to it.

It would be nice if for Admin, a notification can be displayed like: 'In order to send emails, please configure Mail Sending settings' with a direct link to Mail Sending section from Administration (screenshot idea attached).

For a regular user, should be displayed a message like 'Email(s) cannot not be sent. Please contact your Administrator'.

A notification message with a direct link to Mail Sending section should be displayed also on the error message box when sharing a page.