SES refuses to send email from own domain even though domain and email address are verified + no sandbox

Question

I have added my own domain (a namecheap domain) to AWS SES and created the CNAME records at namecheap about a week ago to use Easy DKIM. I added an email address to SES within this domain, say [email protected], example.com being the aforementioned domain. Both were successfully verified by AWS as it can be seen by the green checkmark (and the region is correct):

However, when I want to send an email from this domain via boto3, I get a MessageRejected error:

An error occurred (MessageRejected) when calling the SendEmail operation: Email address is not verified. The following identities failed the check in region MyRegion: arn:aws:ses:MyRegion:MyAWSAccount:identity/[email protected].

The region is correct and my account is not in the sandbox anymore. It works to send from an existing email address outside of the domain, for example my gmail email address.

How can I send emails from my own domain?

Here is the relevant code:

ses_client = boto3.client("ses")

source_email_address = "[email protected]"
destination_email_address = "[email protected]"

response = ses_client.send_email(
    Source=source_email_address,
    Destination={
        "ToAddresses": [
            destination_email_address,
        ],
    },
    Message={
        "Subject": {"Data": subject, "Charset": "utf-8"},
        "Body": {
            "Text": {"Data": email_txt, "Charset": "utf-8"},
        },
    },
    SourceArn=f"arn:aws:ses:MyRegion:MyAWSAccount:identity/{source_email_address}",
    ReturnPathArn=f"arn:aws:ses:MyRegion:MyAWSAccount:identity/{source_email_address}",
)