It sounds like your mailbox index might be out of sorts. You could try going into Domain Settings>Accounts, highlighting your account, then clicking ...>Reindex to see if that resolves the issue but you'll want to give it some time to finish reindexing the mailbox contents before you retest. If you're not currently on the latest public release this might be worth a try as well. If that doesn't work you might want to get a ticket created with us so we can help investigate. 

Good morning,

Thank you for the response, even if I can't find how to do this.

am I in the right window?

Freddy, You are in the settings. You have to go into "domain settings" 

Is the account you are in a domain admin ?

Here is what you do.