SquirrelMail is a mail client, it talks to a mail server, fetches your mail,
displays your mail, and does all the nitty gritty work for you. This is also the
case with Outlook. It is a mail client. It talks to the mail server, fetches the
mail, and does all the nitty gritty work for you. Outlook cannot talk to
SquirrelMail because SquirrelMail itself is a client and not a server.
The best people to ask for the IMAP server settings your Outlook client needs,
are those with whom you are getting your mail services from. If you're not quite
sure, try hunting around the website you signed up on for support pages, or if
you are at a college, or university, speak to a teacher. There's no point in
contacting the SquirrelMail project team - the don't know the which settings you
need.