Importing or uploading email addresses from your email service provider to personalize email marketing is not supported, as in practice these would be useless to Nosto. The exception is importing emails in order to create a custom audience and segment for Nosto Facebook and Instagram ads.
Why Email Import Is Not Supported?
Nosto needs to associate a user and his visit & shopping history to an email address based on user's interaction and history on the site. In other words, if you would upload an email address, we can't associate and process what that user (email address) has done on the site previously. On the contrary, if Nosto has already has tracked the same user's history, we are able to produce personalisation for emails without importing emails.
As a side note, identifying a user based on email address is not needed to provide personalized shopping experience on-site or for Facebook ads, but it is required in order to dispatch an email or to personalize recommendations in Email Widgets.
Difference Between Nosto and ESPs
Nosto is not an email service provider and won’t replace a need for one such as Mailchimp, Bronto or Dotmailer, which allow sending manual recurring emails such as newsletters and similar. However, Nosto’s personalisation elements called email widgets can be easily attached to an any email on any email engine providing advanced personalisation options for each. Read more about the email widget feature here.