Credentials and server info for connecting to an IMAP server.
IMAP server hostname (e.g. "imap.mail.me.com")
IMAP server port (e.g. 993 for TLS)
Whether to use TLS (true for port 993)
IMAP username (typically the email address)
IMAP password (app-specific password for Apple)
Credentials and server info for connecting to an IMAP server.