Going from R 5.09 to R 6.5.1

I posted before but never recieved any replies so here goes again

Has anyone done an upgrade from R 5.09a to R6.5.1 on AS400?

I got 5 partitioned servers running, and am getting ready to do the upgrades, I just wondered if

anyone had already done it and had any problems, or things to watch?

all the servers are used for is email only no development/web services