Can't send emails from Outlook Express Yahoo Mail.

I cannot send emails but I can receive them.

I can receive but can't send them 99% of the times. Once in a while some emails do go out.

Here is what i have:
Outlook Express 6.x
windows xp home with sp2
IE 6..0.2900.x

My outlook Express configuration is as follows:
Identity 1
---------
Yahoo account 1 (sbc yahoo dsl account equivalent to mail plus account) can receive and send some. My ISP provided this email account in collaboration with yahoo.
Incoming mail server is POP3 -> pop.pacbell.yahoo.com
Outgoing (smtp) smtp.pacbell.yahoo.com
Server requires authentication CHECKED
Outgoing Mail server port: 25
Incoming Mail Server port: 110

Hotmail Account can send as well as receive emails - works fine.
mail server is HTTP
Server URL: http://services.msn.com/svcs/hotmail/httpmail.asp

Gmail Account can receive all. have problems sending sometimes.
Incoming mail server is POP3 -> pop.gmail.com
Outgoing (smtp) smtp.gmail.com
Server requires authentication CHECKED
Outgoing Mail server port: 465
Incoming Mail Server port: 995


Identity 2
----------
Yahoo account 2 (Mail plus paid account) can receive email and send rarely.
Incoming mail server is POP3 -> pop.mail.yahoo.com
Outgoing (smtp) -> smtp.mail.yahoo.com
Server requires authentication CHECKED
Outgoing Mail server port: 25
Incoming Mail Server port: 110

On Sending I usually get the following
Socket Error: 10053 Error Number: 0x800CCC0F

Any help will be really appreciated. Hopefully