Well, the login data used through webmail can be different then through an email client.
f.e. some webmail clients want firstname.lastname@example.org
as username .. others want only username ..
email clients normally only want username
password remains the same
server: ip/hostname your mail server is running on
user: username (without @domain.tld)
pass: same as you use for webmail
type: pop/imap (whatever you want)