Unfortunately electronic greeting cards or e-cards are often abused all over the internet. Cards from legitimate e-cards are sometimes used to spam people directly, some e-card services harvest the email addresses that they’re given to spam later, and of course less-than-reputable e-card vendors will spam or even go so far as to include malware (viruses and such) in the delivery.
As a result many email providers now take any link to an e-card as a sign of potential malicious intent or spam, and either filter the message to the recipient’s junk mail folder, or reject the message outright. When e-cards were allowed on Corgi-L, and if a message was rejected by the recipient’s email service it turns out that ListServe could elect to unsubscribe the intended recipient from Corgi-L. This could happen even from popular and fairly well respected e-card services.
Not a very nice greeting at all.
As a result we’ve had to make the decision to no longer accept e-cards in any form (direct send, or links).
Given the way email services are handling e-cards, you might also want to reconsider using them elsewhere since it appears they stand a high chance of not getting delivered.