Do you have email marketing included in the package? If so, how does it work?

I am looking to do email marketing (up to 1000 emails).  Does jotform have this, or does it link with Mailchimp, Constant Contact?  

f so, how does it work?

I'm not sure if this is exactly what you're looking for but we have an Email Newsletter App.

However, you may also integrate your form with other email marketing services like MailChimp and/or Constant Contact.

Regarding your question on how does it works, I would suggest you check out these guides and use it as references: 

How-to-Integrate-with-MailChimp

How-to-Integrate-Form-with-Campaign-Monitor

How-to-Integration-Form-with-Constant-Contact

How-to-Integrate-Form-with-Aweber

I hope this helps. Please let us know if you have any further questions. Thank you.