I have lost my hotmail account on my MacBook Pro How can I retrieve it

This may happen due to hotmail server down. Please check your credentials as well under accounts>properties. If no success after some time, then could try adding another account under
accounts > Email and see if that works.
Hope this helps.

You'll need to change the account's password within hotmail. To update it in the mail app, just locate the account and update the details within the preferences of the mail app.

what is the error is coming exactly?

See if steps 1 & 2 help you...
http://answers.microsoft.com/en-us/windowslive/forum/livemail-email/how-can-i-solve-synchronization-send-and-receive/dee0c2d9-998c-472e-aac9-0374c082854b

Depends if you are using the mail client .. if you are .. you can just go to the sent folder.

If you used a web browser to send your mail, just log into your account and go to sent mail as well.

Possible that the default settings for sending mails is set to the Hotmail account, if you hve to change the default then you might have to take the internet settings and change the default.

i used to run into this when i was in school. im pretty sure its something to do with the server settings allowing non-administered computers that are running on the server to send out connections or mail for some reason. so im guessing the solution would be where ever you created the server from

Check your account settings and make sure your incoming mail server is set to what your ISP requires.

how to set the account up