Ed bought a new Mac and transferred all of his data and email accounts from his old Dell. But now he's not getting all the text of his emails. Leo says that this may be an email provider issue. Apple comes with a fully capable mail program. Leo says to go into the account settings to make sure everything is entered properly. Also, if his ISP is using POP instead of IMAP, it's downloading all of his email and then deleting it from the server. If using POP Mail, it's possible that Ed is only getting new email, not the old ones because they're gone. Leo says that if the emails aren't displayed with attachments or HTML, that could mean that any attached text would not appear.
Leo also has a hunch that all of his email is still there. Ed should check in his settings for "Load Remote Content in Messages." He should also try logging into his email via the webmail interface and he'll likely find it there.
Another option is to get a Google Mail account and have that gather his Cox mail. Then he can access it from Apple's Mail app.