Do you always need an email marketing platform like Mailchimp or Active Campaign to send a HTML designed email? You can actually use Gmail to send them as well. Emails sent directly from Gmail are much more likely to reach primary inboxes than ones sent from an email marketing platform.
You can't just copy and paste your email design into Gmail though. Even though it looks fine in the draft window, its formatting might get messed up after you send it. Here's how to send a HTML email with Gmail properly, step by step.
This method works in Google Chrome, Firefox and Internet Explorer.
You can send the HTML email to yourself with Litmus PutsMail first and view it on a few different email clients (desktop, mobile, app) to make sure the design looks as expected.
You can use a browser extension like Streak to know if your contact opened your email or not. You can also use a tool like Gmass to send your HTML designed email to a list of contacts with names and other details personalized for each recipient.