"Relaying Denied" error for clients sending to our BT hosted domain

[DSLBTForum]

Hi,

I've had the following reported to me by one of our clients (I've not shown our real domain..) :

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Diagnostic information for administrators:

Generating server: CO2PR0501MB904.namprd05.prod.outlook.com

name1@ourdomain.co.uk
ibmr.btconnect.com #<ibmr.btconnect.com #5.0.0 smtp;550 Relaying denied > #SMTP#

name2@ourdomain.co.uk
ibmr.btconnect.com #<ibmr.btconnect.com #5.0.0 smtp;550 Relaying denied > #SMTP#

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This is our mxtoolbox domain listing:

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mx:ourdomain.co.uk   Find Problems 

mx

Pref Hostname IP Address TTL  

1	ourdomain-co-uk.mail.eo.outlook.com	213.199.154.23	60 min	Blacklist Check      SMTP Test
10	ibmr.btconnect.com	213.123.20.92	60 min	Blacklist Check      SMTP Test

dns lookup

dns check

whois lookup

spf lookup

Reported by dns2.register.com on 4/14/2014 at 4:32:41 AM (UTC -5), just for you.  (History) 

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Can you help or do you need more information?

Thanks,