Hi there!
For sending out emails from Converkit, All marketing emails should be sent from a domain you own, not from a personal account at a provider domain, like @gmail, @aol, @hotmail, @yahoo, etc., if you use those emails; this may negatively impact your deliverability.
For your reference:
Why do I need my domain to send emails?11
If you are already using a domain email and still ended up in the Spam folder, I recommend you email help@convertkit.com13 to look at your account.
Thank you!