cluster2a.eu.messagelabs.com "Connection timed out"

Hello,

I have problen to send mail to customers using the solution symantec, my zimbra recive 

cluster2a.eu.messagelabs.com[85.158.139.103]:25: Connection timed out

cluster2a.eu.messagelabs.com[216.82.251.230]:25: Connection timed out

My ip 187.103.250.29 don't  listed on any blacklist.

Thanks,

Marcos Carraro.