This article is nonsense. The author isn't saying anything substantive about the "security" of this particular company. It should go without saying that email backup services will currently, in most cases, need to store your email login information in a retrievable way.

A slightly better post might have been,

"Beware unproven email backup services. Don't forget that if they make a mistake, potentially all of your email messages can be exposed to someone else. Since you probably have account credentials for other services stored in your email box, that situation can get ugly really fast."