In the three years since I was a novice like you, I have come to the conclusion that websites which provide such free services (and I include e-greetings card websites in this) MAY be mainly interested in collecting lists of 'live' email addresses.
In the past, although many e-greetings cards I sent were delivered, it appeared to be a bit of a lottery. It was rare to get a satisfactory response to any complaint I made. There was, however, a noticeable increase in spam mail after using some of these 'free' services.
Always use a disposable email address for dealing with sites like this, and keep a 'personal' address available only to friends, family etc. This should hopefully restrict spam to the disposable address, but it can still find its way into a personal inbox sometimes.