Please look through the list to the left and pick the email client that matches the one you use. These instructions are focused on using IMAP to manage your email and SSL on outgoing mail. IMAP is nice because it allows you to have a full copy of your email over multiple devices, like your PC, our webmail, and your phone.
If you want to use POP instead and keep all your email on your home computer, and under your complete control, simply pick POP versus IMAP as the account type and replace the server name mail.dcn.davis.ca.us with mail.dcn.davis.ca.us.
These setting should work fine for omsoft.com users, who may also use mail.omsoft.com as their POP server