How to send bulk-mail confirmation to authors in several steps?

I want to send bulk e-mails to authors of accepted contributions now and to authors of late submissions later.

If I send the bulk mail to all authors whose submissions have already been accepted, will it then be possible for me to send to authors with accepted late submissions separately - without  those who were notified in the first e-mail being spammed the next time I send a bulk e-mail to all authors whose submissions have been accepted at a later stage?

You have several filtering options when you send bulk e-mails to authors.

Please go to this page:
Overview => Bulk E-Mails => Send E-Mails to Authors (and Co-Authors)

• Go to the filter "Acceptance Status Update Date" and choose a filter that reflects the time frame in which you changed the acceptance status for the submissions (see image).
• You can also create a second "accepted" acceptance status here:
  Overview => Settings => Manage Acceptance Statuses
  Call it for instance "Accepted Late", assign that status for late accepted papers and use it as a filter setting for the option "Acceptance Status" to send e-mails to authors of corresponding submissions only (see image).

You find more information on how to send bulk e-mails here:
Sending Bulk E-Mails with ConfTool