Saving email addresses
You might as well do it right and use webform. It will literally take you minutes once you figure it out.

And then for the ecard submission, you could install the rules module and pass the form values as tokens (including the email address) telling rules that when a webform with the id of "supid_ecard" is submitted, fire this rule -- http://drupalcontrib.org/api/drupal/contributions!rules!rules.module/function/rules_invoke_event/7

All you'd need to do is setup a custom module with hook_rules_event_info() to tell Drupal about your rules, hook_token_list() to list out your tokens, and hook_token_values() so it knows how to render your tokens. Or use the tokens already available.