I've been working with Sendinblue for a day now, and there's some things worth sharing here:

The Bad:
- Their WordPress plugin. If you're using a SMTP plugin like WP Mail SMTP, just don't do it. Sendinblue's plugin will try to divert all your mail through their SMTP server. You can toggle it, sure, but WP Mail SMTP will scream bloody murder about having both on there.
- Their other WordPress plugin (the one that integrates with WooCommerce). It broke my site and needed to be removed. Awesome. Not off to a great start, are we?

A lot of people like these plugins, and its pretty cool that you can override your normal WP template emails with templates you build in Sendinblue; I gotta give props for that. It's just not going to work for me. I'll integrate my contact list another way. Skip.

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UI/UX: It's not great. I mean it's not bad, but it doesn't have the friendly polish that a Mailchimp user will be used to. Don't get me wrong, I didn't expect it to be eleventy billion times better than Mailchimp, or even equivalent, but it's worth noting that there WILL be some adjustment here if thats where you're coming from.

Crafting Emails: I mean it works fine? It's a bit clunkier than Mailchimp's more polished builder, and it's missing things like Mailchimp's much deeper integration with WooCommerce and ability to simply 'add product' when building an email.

Verdict: I think I'm going to pass / return it. I wanted to love it, in no small part because of the savings that I'll get for a year and the savings I'd get per month after the year's up (70-ish CAD vs 79 USD for Mailchimp)... It's just missing some of the features that I've grown accustomed to with Mailchimp. Also the fact that its plugins and my site don't love eachother was cause for concern.