Go to Tools, Accounts, select that mail account, Properties, Servers.
Make sure that "Log on using Secure Password Authentication" is not
If that setting was already unchecked, which antivirus are you running?
Some of them cause problems with Windows Mail over time.
Gary VanderMolen, Microsoft MVP (Mail)
Microsoft MVP Program: http://mvp.support.microsoft.com
"Twist" <Twist@newsgroup> wrote in message news:20AA8E04-430E-4080-AFF5-E03AE730D181@newsgroup
>I am repeatingly having to add my credentials yet am unable to receive or
> send any emails out of windows mail... below is the error message
> Account: 'Vodafone', Server: 'pop.vodafone.co.nz', Protocol: POP3, Server
> Response: '-ERR Invalid command.', Port: 110, Secure(SSL): No, Server Error:
> 0x800CCC90, Error Number: 0x800CCC91
> I have been using this for a while now and all of a sudden it starts to do