Submitting articles to the HubSpot blog is not something readily available. Currently (as far as I am aware) the posts are compromised of HubSpot employees, invited guests, and HubSplot Platinum and Diamond Partners.
If it's really great content, I'd suggest trying to get the attention of some HubSpotters, but that isn't something that will happen overnight.
Best of luck!
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Josh Curcio HubSpot support and inbound marketing for OEMs, contract manufacturers, and industrial suppliers. HubSpot Platinum Partner & HubSpot Certified Trainer