There are no restrictions against a company emailing its existing customers or anyone who has inquired about its products or services, even if these individuals have not given permission, as these messages are classified as “relationship” messages under the CAN-SPAM Act.
(iii) to provide—(I) notification concerning a change in the terms or features of;
(II) notification of a change in the recipient’s standing or status with respect to; or
(III) at regular periodic intervals, account balance information or other type of account statement with respect to, a subscription, membership, account, loan, or comparable ongoing commercial relationship involving the ongoing purchase or use by the recipient of products or services offered by the sender.
In Australia we have what is know as Inferred Consent.
Which means if you have done business in the past there is reasonable expectation you will contact a customer in the future.
What this means to the email marketer is do not be afraid to contact past, existing clients with new offers on your products and services.
Cheers and Great Selling