Relayhost not being used

[Simon Powell]

Hi All
I mailed in a few weeks back as kolab had stopped using my relayhost  
and was trying to deliver mail directly   - I then had total LDAP  
meltdown but I have fixed this now ( thanks to all who helped -  
between the suggestions I got it fixed!).
However my problem persists. In my postfix/main.cf I have the  
following line:-

# Check if there is also a relayport otherwise put the default
relayhost = [smtp.my.relayhost.com]:25

Which is as standard as I have used in the myriad postfix servers I  
have setup over the years - however mail insists on going straight out  
of the server itself and on to its recipients, 9 times out of ten  
getting rejected as I am on a dynamic IP connection. Anyone ever seen  
this before as it's got me foxed.......
Cheers in advance
Si