Transactional emails sent with API taking a day to send

I’m testing the free tier to see what it’s like to send emails with the API (hoping to suggest a. subscription to a client when done if all goes well) and I sent emails yesterday and they all looked like they sent but the were never received.
Today they started arriving to my inbox, and I can see the ones that had errors in the logs also now.
I’m using python, and the code is essentially this that does the sending:

send_smtp_email = sib_api_v3_sdk.SendSmtpEmail(to=to, html_content=html_content, sender=sender, subject=subject)
api_response = api_instance.send_transac_email(send_smtp_email)

Should it take a day for them to send or is there a setting I am missing somewhere?

Hi @deadl0ck , thanks for posting on this community.

Indeed, that’s weird, there should not be a delay like this one. Maybe @Mauricio you know more about this?

Hi @deadl0ck , where you using an authenticated/valid domain when you got the errors?

Hi @Mauricio - yes, it’s validated:

I tried it again just now and it’s working in that I get the email almost instantly.

I’m glad it’s working now. Did you authenticated your domain from the very beginning before you started sending?

Yep - I was fully authenticated before sending anything