MIAMI (CBS) – A consumer group is advising shoppers to think twice before agreeing to have their receipts emailed to them.

The Consumer Federation of California says once a store gets your email address, it can, and likely will, send you more emails, use it for marketing purposes, and possibly sell it to data aggregators.

It’s illegal in California for merchants to collect customer’s private information, like an email address, to complete a credit card transaction.

But, Richard Holober, of the Consumer Federation of California, says stores are getting the coveted information anyway, when a customer willingly hands over their email address for the receipt.

Proponents of digital receipts tout their convenience and contend they are better for the environment.

Apple, the store that pioneered the idea of the e-receipt told ConsumerWatch it does not sell customer’s email addresses to third-parties.

It said it does, however, use them for marketing purposes. Macy’s, another store that offers digital receipts, did not reply to our questions about what it does with customer’s mail addresses.

So, what’s a consumer to do? Holober contends consumers should weigh the pros and cons and “make the right decision.”