09:15 Our monitoring shows higher than normal load on one of the Zimbra mailbox servers, mbox3 - we are investigating the cause. This started at just after 9am this morning. We have received reports of slow response when using webmail.

10:45 UPDATE

We believe we have resolved the issues causing problems with mbox3 - webmail is now working (since 10:30) although response times are likely to be a little slower whilst usage settles down. We are monitoring the server closely and will post a further update once we are satisfied that the issue is fully resolved.

13:30 UPDATE

Shortly after 10:30 GMT server load on mbox3 returned to normal and has stayed there since.  Changes were applied to mysql and Zimbra (memory settings, cache configuration, and connection values) at 10:30 and we believe these changes resolved the problem however we're still investigating.

Please accept our apologies for this mornings trouble.