Check your email for sumpter, hl2dkm or refresh via webmail. Roundcube looks nicer, Squirrelmail is simpler and has an option to change your password under Options > Change Password.
Squirrelmail Webmail (including password change)
These settings work for sumpter, hl2dkm and refresh
You can also use STARTTLS security on ports 143 (IMAP) and 587 (SMTP) if you wish