GHL should have it's own email warmup tool to replace 3rd party providers like Warmy, Instantly, Mailreach, etc. These apps charge ~$49 per month or more to AUTOMATICALLY send, receive, and mark 'Not Spam' emails from a dedicated domain (which we already set up in GHL). They also gradually increase sending volume over time to keep domains safe from blacklisting.

I suspect GHL could replicate these services for less. But, if that's not possible, perhaps GHL can offer integration (and group pricing) with one of these providers.