groupwise 2014r2 very slow and deleted mails are comming bac

Hello,

This is my little config:
1 server sles 11 sp4 virtualised on xenserver 6.5
2 domains
domain 1 has 1 post office
domain 2 has gwia
user: 6 (yep 6 users)
all data is mounted from a iscsi volume
ext3 without H-tree is ative.

Problem:
Sinds a while (6 mounts or more) the system si very slow.
When we change folders or proxy user, we have to wait.

When we use webmail, we got scripts errors because the interface is slow.

I want to delete some mail (750 items) white ctrl a and shift del.
The mails are gone, but the couter unread mails stays.

When we relaunch the client, alle mails are back.

Can someone point me to the right direction?

best regards,

Roel Niesen