Error message when trying to send mail

I get the following message when trying to send mail, using Microsoft mail on
Vista (it was fine until today!). Windows help doesn't open properly, hence
this post.

"The message could not be sent. The authentication setting might not be
correct for your outgoing e-mail [SMTP] server. For help solving this
problem, go to Help, search for "Troubleshoot Windows Mail", and read the
"I'm having problems sending e-mail" section. If you need help determining
the proper server settings, please contact your e-mail service provider.

The rejected e-mail address was 'xxx' [edited for privacy]. Subject 'JASC
7', Account: 'mail.iom.com', Server: 'mail.iom.com', Protocol: SMTP, Server
Response: '550 You must SMTP Authenticate before sending to 'xxxx' [edited
for privacy], Port: 25, Secure(SSL): No, Server Error: 550, Error Number:
0x800CCC79"

Hope someone can help.

"Andy Roo" <Andy Roo@discussions.microsoft.com> wrote in message
news:2A96D642-44A0-4DD2-BEF5-DD353D46CF2F@microsoft.com...
>I get the following message when trying to send mail, using Microsoft mail
>on
> Vista (it was fine until today!). Windows help doesn't open properly,
> hence
> this post.
>
> "The message could not be sent. The authentication setting might not be
> correct for your outgoing e-mail [SMTP] server. For help solving this
> problem, go to Help, search for "Troubleshoot Windows Mail", and read the
> "I'm having problems sending e-mail" section. If you need help determining
> the proper server settings, please contact your e-mail service provider.
>
> The rejected e-mail address was 'xxx' [edited for privacy]. Subject 'JASC
> 7', Account: 'mail.iom.com', Server: 'mail.iom.com', Protocol: SMTP,
> Server
> Response: '550 You must SMTP Authenticate before sending to 'xxxx' [edited
> for privacy], Port: 25, Secure(SSL): No, Server Error: 550, Error Number:
> 0x800CCC79"
>
> Hope someone can help.

Tools | Accounts
Select the account.
Click Properties.
Go to the Servers tab.
In the Outgoing section click the box for My server requires authentication.

--
Frank Saunders, MS-MVP OE/WM
Do not send mail.