Design Automated Email Sequence for Updating B2B Customers on Monthly Spend Progress vs Target

We currently have a loyalty scheme that consists of 3 different pricing tiers, based on a customer's spend for each quarter, and within those tiers are targets that when reached, trigger a volume rebate for the customer. I want to somehow be able to run an automated email blast at the end of month 1 and 2 of each quarter, updating each customer on their spend progress vs the target, and a 3rd email to be sent 3/4 of the way through the 3rd month of the quarter updating the customer on their progress together with how much further they need to go to reach their next target. The data input for this would be a couple of spreadsheets - one with the following columns: unique customer ID, a company name, contact first and last name, and email address. The second spreadsheet would have the company unique ID and their period-to-date spend. The solution will need to collate this data and present it in a meaningful and attractive manner, much like the updates you would get from an airline frequent flyer program every month. I don't have any bias towards a particular email software, you will be required to recommend a solution that is in compliance with all Australian laws in regards to emailing, and that can send from an email address that is linked to our domain. Contact me if you require any further clarification.