Hi good day, i would like to ask how come the emails the we send from our systems gets rejected from our clients using KPN as their mail service.
reject message as shown below
<client>.kpnxchange.com rejected your message to the following email addresses:
<recipient_email>
A problem occurred while delivering your message to this email address. Try sending your message again.
<client>.kpnxchange.com gave this error:
Mail rejected.
Diagnostic information for administrators:
Generating server: VE1PR10MB3376.EURPRD10.PROD.OUTLOOK.COM
<recipient_email>
<client>.kpnxchange.com
Remote Server returned '550 5.0.0 Mail rejected.'