Restricting which posts get sent out to my subscribers

I am sure this is a very easy solution, alas I am stumped at finding it myself (and I have tried).

I am now using an external newsletter client to update my subscribers as opposed to the usual update per post that was fine for some months.

I am trying to work out if there is a way to pick and chose which posts get sent to my subscribers… i.e only news gets sent and not “products”. I want to be able to add new posts to my homepage slider without them being sent to the mailing list.

is this possible ?

Many thanks… sorry if this is REALLY obvious or easily solved.