If:
then please use https://webmail.csail.mit.edu/horde/ to read your email and/or change email filters.
WARNING: Do not ever type any CSAIL password into a form on a web page unless you are absolutely certain The Infrastructure Group at CSAIL manages the web page and the server it's on! See Phishing Attempts on the TIG site for more about this. In particular, there are only a tiny number of pages, listed at Legitimate Password Requests on the TIG wiki that you may ever type a CSAIL password into. Look at that list now — if anybody tries to tell you to type a CSAIL password into any other page, they're trying to break into your account!
This server also lets you create and manage server-side email filters (sending mail from particular correspondents or with particular subjects into their own folders, for instance). To do that, choose "Filters" from the "Mail" menu after logging in. But to turn on or off spam filtering altogether, adjust your whitelist or blacklist, or adjust the threshold at which a message is considered spam, go here.
Password problems? The password this server asks for is not your CSAIL Kerberos password. If you need to, you can change your CSAIL IMAP password at the password change form on the CSAIL IMAP server. (You'll need to log in with your CSAIL Kerberos password to do so.)