There are a few ways to achieve the deletion of all messages older than a certain date.
My preferred choice is to select folders and for those folders to use the Archive old messages function. This will create year by year sub-folders in the Archive and move all messages older than 90 days to those year by year folders. You can then look to delete any of the older folders you wish.
This will keep in the Inbox the most recent mail messages and you can always look in the Archive folders for earlier 2024 and 2023 messages.
Alternatively the Search function has the ability to search for mail messages older than a given date. Just enter the date in the Before box and you'll be presented with the results. You can select and delete all displayed messages. You'll need to keep doing the Search and delete as the displayed messages are just the first page of many.
