You can easily archive emails older than 90 days through your webmail. The archiving will sort the mail into a separate folder. From there if you like, you can choose to delete messages of a certain date, or simply keep them archived.

Step 1

Click the folder you would like to archive. Next,  click the 3 dots, and then click Archive Old Messages.

Step 2

Click Archive.

Step 3

Your mail is now being archived. In a few minutes, refresh the page, and your mail will be sorted into the Archive folder, which is then broken down into years. You can now choose to delete certain years if you like. 

You can also click on a year, then click the 3 dots, and move the contents back into another folder if you would like to move it back.