Yes you should be able to..
POP access isn't always available with the basic free accounts, though
Yahoo - you have to subscribe to the
Mail Plus service in order to have POP access to your Yahoo mail.
Gmail -
POP access is included at no charge.
MSN/HotMail -
... does support Outlook access with their free accounts... no, wait- they
don't support it anymore... but, um... now they
are supporting again. Krikey! MS has waffled back and forth on POP/HTTP access to their free accounts so much in the past few years that I don't even know where they stand today. If they
are currently offering the feature with free accounts, I wouldn't lay bets on that being true 6 months from now.
There
are third-party solutions which can provide POP access for free web-based email services which do not normally offer that service, but obviously, these solutions are definitely not supported by Yahoo and the like.
There are certain limitations to using POP access in Outlook to access web-based email service as well, and many people find these limitations frustrating.
For one thing, there is no correlation between the "personal folders" that you can create in your web-based account, and those you can create in the version of Outlook on your local computer. They are entirely separate beasties, and mail stored in a custom folder created in your webmail account will not be accessible by Outlook.
This can have irritating repercussions. For instance: say that, in your webmail account, you have created filter rules which sort your incoming mail into folders other than your inbox (technically called your POP mailbox). That may work well for organizing emails on the web-based side of things, but because the filtered messages no longer reside in your POP mailbox, Outlook will not be able to read/retrieve them off of your mail service's POP server. Bummer.