Usually, this error is fixed as follows:
In Outlook Express, try using Clear Text, which is the Log on using
option under the Servers tab of the mail account.
To do so:
On the Tools menu, click Accounts. This will bring up several tabs.
If you select any listed mail account, the properties will have a
Servers tab with the Log on using option.
Select the Clear Text option.
If this works, then you were trying to access a non-existent mailbox
or the wrong mailbox. If this does not work, then the administrator
needs to check for and remove the custom recipient.
If that does not help, additional research might be in order.
Have you ever tried to login on this account with these parameters?
Best regards,
Doncho