Windows Live Mail cannot send, but it Receives OK
All e-mail programs (including Windows Live Mail) use one port to send messages, and a different port to receive them.
This error, where you can send but not receive (or the other way round), is a classic sign that you are specifying the wrong port number for the one (send or receive) which is not working.
Don't make the mistake of assuming that because you didn't alter the e-mail settings, the port number can't have changed. Corruption can occur from many causes.
These account settings aren't stored in the Windows registry. Each account has a configuration file called account{GUID}.oeaccount in the account's folder within the store folder (i.e. a file with the file type .oeaccount).
I've never actually known an .oeaccount file get corrupted, but there's always a first time.
It's an XML file (readable in Notepad), which contains all the account settings. These settings are viewable in the account's Properties: in the left-hand folders pane of Windows Live Mail, right-click on the e-mail account's name (e.g. someone @hotmail.com), then click on "Properties". The settings are found on three of the tabs there: "Servers", "Advanced" and "IMAP".
Check that your settings are correct.
The following settings are what you need with Hotmail.
If you use something other than Hotmail, do a Google search for its settings, but usually EVERYTHING will be the same EXCEPT the server address and port number. Alternatively, the correct settings you need to use will be available on the website of your Email Service Provider.
IMAP Settings (for Hotmail):
Incoming Mail -
Server type: IMAP
Server address: imap-mail.outlook.com (Port: 993)
SSL required: Yes
Authenticate using: Clear text
Logon Username: YourName @hotmail.com { Your details
Outgoing Mail -
Server type: SMTP
Server address: smtp-mail.outlook.com (Port: 25 or 587)
Requires SSL: Yes
Requires Authentication: Yes
POP3 Settings (for Hotmail):
Incoming Mail -
Server type: POP3
Server address: pop-mail.outlook.com (Port: 995)
SSL required: Yes
Logon Username: YourName @hotmail.com { Your details
Outgoing Mail -
Server type: SMTP
Server address: smtp-mail.outlook.com (Port: 25 or 587)
Requires SSL: Yes
Requires Authentication: Yes