Email Server's don't work...

Hi forum,

This is my enviroment:

/dev/da0s1a 581M 34M 501M 6% /
/dev/da0s1e 1.9G 528M 1.3G 29% /usr
/dev/da1s1e 8.3G 7.5G 120M 98% /var
/dev/da2s1e 33G 3.0G 27G 10% /S
procfs 4.0K 4.0K 0B 100% /proc

I get have to mount my partition /var in /S, but while i switch slices from fstab file: (e.g /var--> /S and /S--> /var). My Email Server's don't working.
The Users don't get entry in mailbox from webmail....What it's wrong???

thanks guys...