Messages being deferred, possibly on internal blacklist?

Hi my webserver is having issues sending emails to messagelab clients where the emails timeout when they reach the messagelab servers. The error that is being thrown in the mail logs is "delivery temporarily suspended: connect to cluster4a.eu.messagelabs.com[85.158.139.103]:25: Connection timed out" the IP address of the server is 45.76.231.131. Would it be possible to check if this IP is currently on the internal blacklist as I have seen it mentioned in other discussions over the same issue.

Any response would be appreciated.

Thanks.