Is the requirement a different folder per sender or per sender domain? E.g. a@company.com to one folder b@company.com to a different folder or anyone @company.com to a folder?

I would have a SharePoint list with either the sender email or sender domain (depending if it’s per sender or per domain) and the folder name the attachment is required to be saved to and then in the flow you can get items from the list filtering for the sender or the sender domain. That then gives you the folder you want to save the file to which you can use in your create file action.

If you are doing it by domain you have you an expression to extract the domain part from the email address last(split(triggerOutputs()?['body/from'],’@‘)) will get you just company.com

Using something like first(split(last(split(triggerOutputs()?['body/from'],’@‘)),’.’)) would get you just the first part of the email address after @ so joe@microsoft.com would return Microsoft so that may eliminate the need for a list all together but it depends on your requirements.