Sending large numbers of emails (newsletters or other marketing content) using Send Email or Newsletter Manager is not recommended. Your server and hosting account probably don’t allow for mass quantities of broadcast emails, and doing so could cause you to be treated like a spammer.
Instead, we recommend that you use an Email Service Provider to handle your bulk emailing needs.
Exporting Email Addresses
To export email addresses, use the Email Address Exporter plugin and use it to feed the emails into a 3rd-party provider.
There are several alternatives for sending newsletters and mass marketing messages. The best known service that has a free pricing level is MailChimp. With them you can send emails, generate reports, do automation and more. They offer a few pre-built templates and their free service is sufficient for most small sites. They also have paid features and now position themselves as a full marketing platform.
A MailChimp Integration plugin is available for Zen Cart.
Other providers exist as well, but you will need to do your own integration.
Some names you might have heard of are Constant Contact, SendInBlue, SendGrid, and Sendy.
If you want to look for other options, do a web search for “newsletter provider service.”