To edit your message filters, please start from the "Custom Messages" tab under Communications in your left navigation. Click the title of the message you want to edit, and then click "Continue" at the bottom of the page.
From the next page, in the "Filters" section, click "Show Advanced Filters" in the lower right corner.
The filters "ASIN is Not" and "SKU is Not" allow you to exclude specific ASINs or SKUs from receiving your message. For example, if you want your message to send to all your orders of all your products except for orders of your ASIN "B01XXXXXX," you could enter the ASIN "B01XXXXXX" into the "ASIN is Not" field and orders of that ASIN would not be sent your message. You can also input multiple ASINs into this field and separate them by using a comma with no spaces in between (e.g., "B01XXXXXX,B01XXXXXY"). The same principle applies to the "SKU is Not" field.
Make sure to click "Done" at the bottom of this page to save your changes.
For more advanced SKU filters, please see our article on SKU pattern matching.