[Exim] 504 DNS verification of sending machine failed

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Hi

I have 2 mail server 1 running exim 4.24 and the other 4.10
when trying to send mail to the following domain (egoli.min.wits.ac.za) Iget the following error when using the server running exim4.24
504 DNS verification of sending machine failed

When using the server running exim4.10 it works fine.
Any ides as to what could be the cause of this

Thanks
Cheers
sherona
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