Mac Outlook Express 5.x Error -3170

This error occurs in Outlook Express 5 for one of two main reasons:

1) The POP mail server is set incorrectly in the relevant Tools > Accounts window

Enter the correct POP server details and try again.  Sometimes, the problem can only be resolved by recreating the mail account (in extreme cases, you may even need to create a new Identity).

2) A valid network connection has not been established

Check that a dial-up connection has been established and that the customer can browse.  If the customer cannot browse, look toward the usual troubleshooting methods (clear cache, dump MacTCP DNR, Internet Preferences and TCP/IP Preferences etc.)