I have a Scalix 11.4.6 server running on OpenSuse 11.0 with the latest updates for a long time, but sometimes suddenly users can't log in.
They all use one mailbox (info@...) and all use Thunderbird email client with IMAP. When I restart the server it all works, but without any reason Thunderbird suddenly asks for the password. When I try t log in it doesn't work. Even when I log in to webmail, it says the username or password is incorrect. When I restart the server it all works again, but it can be for a long time but also for a couple of minutes.
I tried different Thunderbird versions, resetting the servers IMAP cache, created a new mailbox and imported the old one but nothing helps.
I don't know why this happened because none of the software (OpenSuse or Scalix) changed. What could be causing this?