OK. I have more data. The slow response in the “users” tab is caused by checking of the size of the mail accounts. When we click to this tab, the system is checking the size of all mail accounts. When the mail account are very big (one account very big, with a lot of little received mails you have a lot of accounts) this error appear. I see that i’m not the only with this problem. See this posts
So i think that this must be fixed in a update. The user “Evgeniy-Bondaren” suggest to put a button that checks the size of the mail accounts when its neccesary (or a button in each account to check the size of one account). Or separate the size check of the accounts from the management of the accounts.
I think that there are two ways to fix it in more elegent way:
increasing the waiting time to check the size of the acccounts
making a script that automatically checks the size of the account every day at night. Write the size of the accounts in a database and show this size the following day for each account.
Meanwile i will try to disable this space check. I’ll continue investigating