Who is your ISP, and why aren't you using your ISP's SMTP server
instead of smtp.fasthosts.co.uk?

Corrupt mail account file.  Happens.  You aren't running Norton  are you?  In any case DELETE the current file entirely.  If you saved/exported the account settings file back when it was working, IMPORT it now.  Otherwise, re-enter the POP3/SMTP info as instructed by your email domain server's instructions.  (Which are you using?  Gmail, Hotmail, Comcast, Yahoo, etc?).  To find the instructions for most domain/ISP's, got online to their HELP section, FAQ, and search for POP, POP3, SMTP, and/or Mail Client.  Pay particular to their requirements for authorization settings.  Once you have it working, EXPORT a copy of the settings (TOOLS>ACCOUNTS>EXPORT) so that the next time this happens, and it will, you can just IMPORT the file and fix it quick and easy.  This lesson learned by Olde Greywoolf the hard way!
Bob, Still Old, Still Grey, And Still A Woolf

No trees were harmed in the sending of this message and a very large number of electrons were asked their permission to be terribly inconvenienced. And a party was thrown for them afterwards for being really cool about it.

Bob's Space - Home Page of the Olde Greywoolf

 Hiya
 Yes my email provider/web provider does offer webmail, but I have had a look
 and it looks very basic - not even a sent folder??
 Hence the reason I thought I would switch over.

 They did come back to me saying the same thing you said about port 25 so
 said to use port 225 instead, which I changed, but still have a problem.

 I have just gone in and when it asked for my username/password, I cancelled
 and it came up with this error message

  Subject '', Account: 'mail.onecallcommercial.co.uk', Server:
 'smtp.fasthosts.co.uk', Protocol: SMTP, Port: 225, Secure(SSL): No, Error
 Number: 0x800CCC17

 Does this make any more sense - really appreciate all the help!

 "robertmiles@bellsouthNOSPAM.net" wrote:

 > You might check if your email provider offers webmail, and if so,
 > try logging in using that.
 >
 > Does your connection to the server cross over from one internet
 > provider's equipment to another's before it reaches the server?
 > If so, connections to port 25 are often blocked to cause trouble
 > for spammers, and occasionally connections using a few other
 > ports as well.  In such a case, you would have to ask your email
 > provider to make connections using some other port available,
 > and give you the details.
 >
 > Occasionally, if the server keeps asking you to log in, you can
 > click Cancel, get an error message, right click on the error
 > message, copy all of it to your next message to this newsgroup,
 > and give us some more ideas.
 >
 > "deb960" <deb960@discussions.microsoft.com> wrote in message
 > news:6D935255-5B24-4310-8ED7-18B8A28D7323@microsoft.com...
 > > Hi again
 > > Thanks - have tried all variations but with no avail!
 > > I even went in and as you said backspaced and deleted and re-entered, but
 > > its still coming up and asking me for it and will not let me pass.
 > >
 > > Not sure if this matters but I am using this mail for my small business -
 > > my
 > > service provider has given me all their pop3 and stmp settings I need - so
 > > dont think this is the problem?
 > >
 > > Any other suggestions?
 > > "robertmiles@bellsouthNOSPAM.net" wrote:
 > >
 > >> Some email servers insist that you enter your username with no spaces and
 > >> no CAPITAL LETTERS.  Some insist that you follow it with the part of
 > >> your email address that starts with @, and some insist that you don't.
 > >> Many
 > >> insist that you use CAPITAL and lowercase letters in the correct places
 > >> in
 > >> your password.
 > >>
 > >> Windows Mail has a quirk that often makes it forget your password if you
 > >> put a checkmark in the box before Remember password, and then in the
 > >> same session, click Apply.
 > >>
 > >> What you find a username and password that works, you can tell Windows
 > >> Mail to remember them by clicking on Tools, then Accounts, then your
 > >> email account, then Properties, then Servers.  If there are already
 > >> incorrect entries for the username or password, click at the end of them
 > >> and backspace over them, then type the correct entries.  Click on Apply,
 > >> then obey any instructions it gives you about entering the password
 > >> again.
 > >> Click on Apply, then Close.
 > >>
 > >> "deb960" <deb960@discussions.microsoft.com> wrote in message
 > >> news:024B3484-B809-463B-A4ED-D206F09FE461@microsoft.com...
 > >> > Hiya
 > >> > Yes I checked the correct STMP and POP3 servers are fine - I also
 > >> > checked
 > >> > the My server requires authentitication.
 > >> > This is where I now am asked to confirm my username and password, which
 > >> > I
 > >> > do, but it doesnt accept it, just keeps asking me over and over again.
 > >> > Is there a way I can re-set these?
 > >> >
 > >> >
 > >> > "Ian6220" wrote:
 > >> >
 > >> >> I had a problem sending email until correcting email settings. Have
 > >> >> you
 > >> >> tried
 > >> >> checking your email settings.
 > >> >>  Open windows mail. Select TOOLS - ACCOUNTS. select your email account
 > >> >> then
 > >> >> PROPERTIES. here you can check settings on the different tabs. In the
 > >> >> Server
 > >> >> Tab i had to tick the box - My Server Requires  Authentication and
 > >> >> also
 > >> >> on
 > >> >> Settings - Use same settings as incoming server. Make a note on any
 > >> >> changes
 > >> >> you make so you can always go back and then try different settings.
 > >> >> Also
 > >> >> check email and password are correct.
 > >> >> --
 > >> >> Ian
 > >> >>
 > >> >>
 > >> >>
 > >> >> > Hi
 > >> >> > I have just set up a windows mail account and I can receive emails
 > >> >> > but
 > >> >> > cannot send them.  When I press the send button - it comes up with a
 > >> >> > box
 > >> >> > saying Windows Security then asks for my username and password,
 > >> >> > which I
 > >> >> > enter, but it does not accept.
 > >> >> >
 > >> >> > All I can think of is that I am entering the incorrect user name and
 > >> >> > password, so how can I re-do these settings?
 > >> >> > Please can you help.
 > >> >> > Thks
 > >>
 > >>
 > >>
 >
 >
 >