Custom getting "Temporary problem, please try again later"

[n000b]

I had a new customer sign up with me recently. He said that his e-mail account in Windows Live Mail works fine, but in Thunderbird it does not. He has tried it on two different computers both running Thunderbird on two separate internet connections, but on both of them he is getting this error when trying to retrieve e-mails:

'Sending the password did not succeed. Mail server mail.example.com responded: Temporary problem, please try again later.'

There is nothing in /var/log/exim_* or in /var/log/maillog about it. I am running Exim and Courier.

I tried setting up his e-mail account on my home computer in Thunderbird and it worked fine, so I suspect that he may have made a mistake with the settings, but he assures me that the settings are correct.

Is there any way that I can get a more descriptive error of the problem?

[thewebhostingdi]

Please make sure that the SMTP Port address is not blocked in the local machine firewall.