Regarding filtering junk-mail, it is recommended using Postini - a service that the College pays for that filters out spam and viruses - instead of Webmail filters. The spam filtering is off by default for all users so people don't inadvertently lose messages, but is straightforward to enable. See Setting up Postini to Block Spam for instructions on how to turn on Postini's spam filtering.
The benefit of this service is that it traps all the spam before it even gets to your account so you don't have to deal with processing each message with a blacklist. You will receive an occasional email (the interval is configurable) notifying you that there are message for you to review at the Postini site.
It's likely that your Webmail is configured to hide deleted messages. You can check how it is currently set by looking in the far right of the tan bar right above your listing of messages. If it is not hiding them, you'll see a link that says "Hide Deleted." The opposite is true if you see "Show Deleted." In any case, you should regularly "Purge Deleted Messages" to clean up unneeded space and improve responsiveness of your mail.
Please verify that you are sending just your username and not your full email address. "username" will work, but "username@whitman.edu" will fail to log in.
The profile editor interface can be a bit misleading. Under "Mail->Personal Information" you need to first choose the identity to modify in the "Select the identity you want to change:" drop-down menu, make the edits there, and finally click "Save Options".
Most likely your screen size is smaller than standard, so you can't see all the buttons at once. In most web browsers, you can send a message by clicking Ctrl-s (that's the Control key plus the "s" key), thereby avoiding the need to find and click the Send button.
Whether you are a recent graduate or staff or faculty no longer working at Whitman, you will have one year to save your Whitman email and netFiles data. A useful guide to transferring such data can be found here.