I also have the same problem. As of now, I do not have problem when sending email to
gmail.com, yahoo.com and hotmail.com.
Also, I installed roundcube.
https://azdigi.com/blog/en/webserver-panel-en/aapanel-en/install-mail-server-on-aapanel/
Do not forget to install first the apache or ngnix, php, mysql, phpmyadmin when installing roundcube because it is also required.
When I send email to this email server, they successfully verified my DKIM, SPF and DMARC.