How send a node as a newsletter by rules in Drupal 7?
I will only provide some pointers as it would take me an hour or more to write out the steps.


It would be best to use Rules scheduler, rather than a views loop to
send this info. Every cron run you don't want to have to loop
through all of your node to check to see if one needs to be sent.
Enable Rules Scheduler.
Create a Rules component with an action of send email. This will
contain all of the email structure including your field tokens for
your node. The to field will be all users of role "INSERT YOUR
ROLE".
Then create a rule to schedule that component when a node is saved.
Use condition "entity has field" to pull your "trigger field" into
scope. Then add a second condition, "Data comparison" or "data is
empty" (negate if needed as I do not know what type of field your
going to trigger this off of).
Set the schedule time to be the current date. Rules scheduler only
happens on cron anyway, so this will ensure the next cron run it
will send.


Note: Rules and more specifically core does not support html emails out of the box, so use something like mime mail, Html mail or mandrill module to do this. If your nodes contain images that need to be sent, then you are going to need to add a special filter for those fields so that add your site root is added to all images and links. This way it doesn't use relative paths and break your images/links. Use the Pathologic module to do this.