How do I configure sendmail for POP/IMAP/…?
You don’t. Sendmail is a mail transfer agent whose primary purpose is to send and receive e-mail (primarily via SMTP). Sendmail does not implement any remote access protocols such as POP or IMAP. But if you want to learn more about these and other (non-sendmail) e-mail related things, please refer to our Other (Non-Sendmail) E-Mail Related Links page.