Which app did you use to do this?
To set up Hotmail using 'Mail by HTC', touch the Mail by HTC icon (it's in apps if you haven't added it to your Home screen) > Menu > Accounts list > New account > and follow the instructions. Select Other (POP3/IMAP) for Hotmail. It should recognise your Hotmail email address so don't bother about manually typing in settings, just click 'Next'.
You can delete the Hotmail account on your phone and try again, which might be the best thing to try as it won't take long to set up another. In Mail by HTC, ensure Hotmail (or whatever you have called your Hotmail account) is shown on the top line of the email screen - it should be just above 'Inbox' if you have that as the default screen it opens on > Menu > More > Settings > Delete account > OK (Check you have the correct account at the top of the screen). Then try setting up the same account using the above instructions.
If you do/did the above and things still don't send, then the issue might be the settings in your 'Outgoing server settings'. In Mail by HTC making sure you have the relevant Hotmail account selected, Menu > More > Settings > Account settings > and confirm the entries are correct before pressing 'Next'.
Incoming settings
Protocol = POP
POP server = pop3.live.com
Security type = SSL
Server port = 995
Outgoing server settings
SMTP server = smtp.live.com
Security type = TLS
Server port = 587
Those are the settings I have on mine.
