Is there any auth SMTP service?
 

For outgoing messages for my domain email which is forwarded by Namesilo.
I know Pobox has that, but 20USD per year is not reasonable to my usage. I send very few messages.

Thanks.

Mailgun? Free for the first 10,000 emails each month.https://kinsta.com/knowledgebase/mailgun-wordpress/

thanks. but all sendgrid/mailgun/mailjet are blocked in my country, as well as google.

Migadu free tier? https://www.migadu.com/en/index.html

let me check it. thank you.