Is MageMail CASL-compliant?
Pre-existing business relationships (for purchases up to 2 years out) seem to be allowed. Abandoned cart emails seem like they are a bit of a gray area.
As always, the decision is ultimately up to you. I'm not a lawyer but I do try to give as much common-sense feedback on issues like this as I can.
You may also be interested in this blog post on how much email is too much.