Motorola Droid X :: Email Configuration - POP3 And IMAP Account

I am having some very annoying email problems that I have fought with for almost a week, researched and tried multiple programs, and followed about every tutorial on this and similar sites to make work. My school system's email provider is junk, but since I'm a traveling teacher (I bounce between schools) it is very important that I be able to receive and reply to emails from administrators and other teachers. I'm coming from five years of Blackberry email, where all it took was inputting my address and password in the BIS email page and never having to give it a second thought.

So far, here's a rundown on what's happened and what I've tried:
1. Using My Accounts and the stock email program, my email address has been added. It will not connect when set up as a POP3 account; I must set it as an IMAP account to retrieve any emails. No matter what port setting I use (25 or 587), I cannot send or reply to email.
2. Using K-9 email, I am able to download email as POP3 with standard settings (port 110). As with the built-in client, I am unable to reply to or send emails.
3. Before you ask, 587 never worked. I've tried.
4. The email address is configured in accordance with our service provider's instructions..
5. This issue has occurred in the same manner on both 2.1 and 2.2.