So what you're saying is that they should limit their market to those users that can successfully set up email forwarding, solely because storing passwords is bad.

Part of the service they're offering is that they'll restore the contents of your mailbox in case of accidental or malicious deletion. I have

    mail:/var/mail/associatedtechs.com/rob@associatedtechs.com# find . | wc -l
    24846

...almost 25,000 messages in my mailbox. How do you recommend that they restore 25,000 messages to my mailbox without my account credentials?