If you resolve smtp.maildoso.com yourself, or run a manual SPF/DKIM/DMARC lookup and compare the result against that hostname, you can see what looks like a total authentication failure — SPF not authorizing the IP, DKIM pointing somewhere unexpected, DMARC failing — even though your domain is set up correctly and mail is delivering fine.
Why this happens
smtp.maildoso.com is a shared front door, not the actual server your domain sends through. Every domain/mailbox on Maildoso is routed through its own dedicated sending host behind the scenes. Resolving the shared hostname and checking its IP (or its DKIM key) against your domain's DNS records compares the wrong host to the wrong record — of course it won't match. This is expected and does not mean your domain, DNS, or deliverability is broken.
How to check authentication correctly
Send a real test email from the actual mailbox in question (for example to a mail-tester.com address, or to your own Gmail account) and read the Authentication-Results header of the message that arrives — that reflects the real sending host, not smtp.maildoso.com.
In Gmail, open the message, click the three-dot menu, and choose "Show original" to see spf=, dkim=, and dmarc= results directly.
If you're checking DNS records themselves (not a sent message), look up the records on your own domain, not on smtp.maildoso.com — see How do I manage and verify DNS records for my domain with Maildoso?
When it's a real problem
If a test email sent from your actual mailbox shows spf=fail, dkim=fail, or dmarc=fail in its headers, that is a genuine issue — contact support with the full message headers (or the mail-tester.com report link) and the mailbox/domain involved so we can look at the specific sending host.