Good free alternative to Gmail Boomerang?

[thanos]

Hello everyone. I'm not sure this is the right topic to answer this question, but I'll give it a shot.
I'm looking for good Gmail extension like Boomerang to schedule emails and make reminders, preferably for free. I need to schedule a lot of work related emails, but can't afford Boomerang because there are other more important things I need to pay for. Thank you in advance.

[Harold Mansfield]

On what device do you use your Gmail the most? A laptop or desktop, and what OS? Or mobile, and what OS?

By the way, moved to Water Cooler since this isn't a blogging question.