Hey @megahuy2
The template source doesn't matter for deliverability. Klaviyo's sending infrastructure, your domain reputation, your authentication setup, none of that changes based on whether the HTML came from Canva or Klaviyo's own editor. Inbox providers don't care where you built it.
Canva's builder is designed for visuals, so the emails it produces tend to be image-heavy with very little actual HTML text. Spam filters can't read text baked into images, so a mostly-visual email gives them almost nothing to evaluate. That's where things go wrong, not the tool itself.
The other thing worth checking before you commit to this workflow: Gmail clips emails over 102KB. Canva's HTML output can be bloated, and clipping is silent. You won't get an error, your open pixel just hides and your open rates drift down over time.
Quick test: push one template, send it to yourself, check the raw HTML file size, and see how much actual text is in there versus images. If it's mostly images, drop a short paragraph of real HTML text in before sending. You can also edit the HTML directly inside Klaviyo after the push to add things like {{ first_name }} since Canva can't inject Klaviyo personalization tags on its own.
I hope this helps.
Thanks,
Arpit