outbound smtp port 25 blocked

Hi

I run a mailserver for a couple of clients.

Outbound to one of their contacts who is using messagelabs is failing

telnet to port 25 of the messagelabs servers from my mailserver mail.dataskill.co.uk 31.193.136.55 although I can telnet in from other IPs

It could be down to incorrect SPF records for my clients domains but these have now been corrected

nt@ls1:~$ telnet 85.158.136.35 25
Trying 85.158.136.35...
telnet: Unable to connect to remote host: Connection timed out

TIA

Nick