Late mail delivery to Zimbra Desktop / Outlook but Instant delivery in webmail
I'm having a strange problem on one Zimbra account. We're having a 25 account licence and set-up. One account is having problems with mail delivery. When receiving a mail, it shows up right away in webmail. But it takes about an hour to arrive in Zimbra Desktop (of course I tried 'get mail'). I configured the account on other internal and external machines (other OS, zimbra desktop and Outlook with connector). I tried reindexing, ... I have no inspiration ...
Can someone help me?
Thanks for your advice,