I have found problem with Zimbra Mail Server.
I connect to Zimbra via Thunderbird but sometime it's slow to show message, many times I found this problem, please advise.
About server specifications;
HP Proliant DL 180 G5
Intel Processors E5420 Xeon Quad Core 2.53
Memory ECC-RAM 2048 MB (up to 10 Gb in soon)
500 GB S-ATA x 4 Raid 5 with HP Smart Array E200/128 MB
all client 50 users.