POBox.com Email being blocked
I have been a subscriber of the POBox.com email redirection service since 1994 and a subscriber of Cox Internet since 1998. I regularly send emails via my Pobox account to my father-in-law who uses Cox's email. The last email to reach my father-in-law's mailbox was December 24, 2023, since then email from POBox has been blocked. I opened a support ticket with POBox and they informed me that Cox is responding with:
250 2.0.0 <firstname.lastname@example.org> sender rejected. Refer to Error Codes section at https://www.cox.com/residential/support/email-error-codes.html for more information.
I do not send spam from this email address, and neither does my wife, whose Pobox address is also being blocked. I am not the owner of the Pobox domain, as it is a commercial forwarding service. I would like to work with Cox in unblocking mail from me, my wife, and other PoBox subscribers.