The "to-do" features that Apple has built into many OS X applications (iCal and Mail) are exceptionally useful for some users that have adopted them. In iCal the to-dos fade out and disappear after they've been completed, but in Mail they persist, which has been a little inconvenient for some users.
Apple Discussions poster Justin Harlow writes:
"When I check a To Do item complete, it doesn't ever go away (in Mail) and I can't find an option to hide them. As a result, one has to look at pages and pages of completed items when all you really want to see is the things that need to be done NOW...You can do this in iCal and every other To Do system I have ever looked at."
In Mail the to-dos all appear in a list in the "Reminders" section on the sidebar. While they are separated under the account in which they were created, the organization of them is rather limited, and as such users who create many of them can end up with huge lists. Currently users have several options to manage To-Dos.
Delete them Users can manually delete completed todos, by highlighting them and pressing the delete key or by right-clicking them and choosing "Delete". This is not too desirable since many users would like to keep an archive of completed items for at least a little while.
Sort them by completion status Users can sort their to-do list by any of the columns at the top of the list, including the check box column. Clicking this column will group all completed items together and have them either at the top or the bottom of the list depending on if the list is in ascending or descending order.
Create smart mailboxes for them This is probably the more complete and desirable method for managing To-Dos, and users might overlook this capability in Mail with the assumption that Smart Mailboxes only pertain to email and notes since this is true for mail rules. With smart mailboxes users can create a mailbox that shows only incomplete to-dos, and likewise can create one that only shows completed to-dos, or those that are in a specific date range, etc. This will make to-do management much easier for users who extensively use the to-do features.