messagelabs.com Connection timed out

Hello

We're experiencing problems when sending to email addresses that use messagelabs.com MX. See below;

Previous Message: 1bQsBx-0005UT-RH: H=cluster3.eu.messagelabs.com [85.158.139.3] Connection timed out

This is happening for various accounts on our server which is sending from IP Address 88.202.228.72

I have used this;

http://ipremoval.sms.symantec.com/lookup/

to check on our IP and it tells there is no problem with the IP Address.

Can you please help us resolve this issue as it's causing me headaches!

Thanks