Send email to a list of customers who have booked during a time period

1. Click View > Web Reports.
2. Under the Marketing section, click Top Customers Report.
3. Pick your date range for bookings.
4. Set Maximum Results to All.
5. Optional.  Set any additional parameters.
6. Click Next.
7. Scroll to the bottom of the results page and click Download to Excel.
8. Using this exported CSV (Comma Separated Values) file, you can use your 3rd party email software.

Mail Merge in Microsoft Word
https://support.office.com/en-us/article/use-mail-merge-to-send-bulk-email-messages-0f123521-20ce-4aa8-8b62-ac211dedefa4