Hi Falko, I was running Virtual Users And Domains With Postfix, Courier And MySQL(with addional Squirrelmail) successfully for over a few years. Since just a while one particular user cannot access his inbox using Squirrelmail. We receive the following error: ERROR: ERROR: Connection dropped by IMAP server. Query: THREAD REFERENCES ISO-8859-1 ALL If I click another folder (drafts, sent mail etc) it displays it successfully. I think it must have something todo with some strange message containing invalid characters or something. I saw the same message in another thread and you adviced to update dovecot, but I don't have dovecot running, I have courier-imap. Do you have any suggestions ? For example, is there some kind of check to see if a imap dir is healthy ?