Yes, these 2 checkboxes are disabled/cleared for webmail.oralab.com. I also checked my bind zone files and see that oralab.com, mail.oralab.com, webmail.oralab.com, www.oralab.com
all point to my host of 172.16.0.67, so I do not believe there is an issue with DNS resolution.
Is there something in postfix that I can verify to find out why e-mail to email@example.com
fails but firstname.lastname@example.org