Undelivered Mail Returned to Sender

I am facing an issue with sending emails. All my mails are coming back undelivered despite putting the correct emails. One example is below. Can someone help, please?

This is the mail system at host mout-p-102.mailbox.org.

I'm sorry to have to inform you that your message could not

be delivered to one or more recipients. It's attached below.

For further assistance, please send mail to postmaster.

If you do so, please include this problem report. You can

delete your own text from the attached returned message.

The mail system

<pkginfo@ups.com>: Host or domain name not found. Name service error for

name=mxa-002b8001.gslb.pphosted.com type=AAAA: Host not found