My server has developed an expected problem where I am unable to connect from a mail client. I've looked at the server logs and the only thing that looks to identify a problem are events like the following: The problem is unusual, because just half an hour previously at my office, I was not being prompted for a correct username and password in my mail client. I haven't made any changes to the server, so I can't understand what would have happened to make this error occur. Searches for the error messages yield various results, with 'fixes' that I'm uncertain of (obviously don't want to make it worse or fix something that isn't broken). When I run I also get the following result: But when I run I get: I found those commands on another forum and am not entirely sure what they mean, but I'm hoping they might give an indication of where the problem might lie. If it makes any difference, I'm running Ubuntu 10.04.1, Postfix 2.7.0 and Webmin/ Virtualmin.