Email being rejected 550 message refused

[ukdeveloper]

So, I run a small whm/cpanel and I have an account for a client who's having real email issues sending to a particular client.

Mail is bouncing with not much of a reason and I have no idea where to start looking. It seems to be the reason of the recipients server as my client is able to send mail elsewhere. However the email which is bouncing is his major client and is also a major company so getting any kind of support from them as to why mail is being rejected is a no go.

The error the raw bounce shows is:

550 5.5.0 550 5.7.1

Requested action not taken: message refused

I know he sends mail from Outlook.

My server isn’t on any RBL’s

So im not sure where to start drilling this down.

Any help would be fantastic. Im quite new to this so any requests should be step by step if possible.

Ive attached 2 files. One shows an email sent which had 4 recipients, which bounced.

the other file shows a SINGLE email sent to the recipient in red on the other attachment which went through fine.

Thanks

UKD

 

[sparek-3]

Unfortunately, only the administrators of the remote server that you are trying to send the message to would be able to tell you why their server is refusing the message.

 

[ukdeveloper]

Its strange because ive also found out just now that if my client sends mail to them, it gets rejected but if he tries again, theres a good chance it will get delivered.

 

[cPanelLauren]

I agree with @sparek-3 here, there's no way to know why it's sometimes being refused and sometimes being accepted from your server. Steps you can preliminarily take might be to ensure that the domain has a valid SPF, PTR and DKIM as well - if you have those things for that domain you'd need to contact the remote admin for details on how to resolve the issue.