Statistics collector collects everything except mail stats?

I have the collect task enabled on my hub server to collect stats from all servers in my domain. My problem is it has always collected everything with the exception of mail stats, it cannot even collect it’s own mail stats.I thought that upgrading it to R6 would help solve it but it did not. It collects data from R5 and R6 servers always with the same result just missing the mail stats.

If I open the Server - Statistics section of the Administrator I can see mail stats displayed so why do they not appear when collected?

Can anyone think of anything that could cause this? Many thanks.