IP warming services - mailwarm.com

Warming IPs and domains is a longstanding issue; has anyone tried services like https://www.mailwarm.com ? I’m not 100% clear on how it works, but seems to be a sort of botnet of gmail mailboxes which automatically interact with your domain in order to improve it’s reputation and deliverability. For a monthly fee, of course. You give them an SMTP login and they do the rest.

Seems to not work solo, however - their mail / interactions must represent only a small amount of the total mail sent from the IP / domain being warmed, it seems.

Hacky / spammy / or practical - thoughts?

There are similar services like:

And there are loads of others solely targeting Gmail it seems: