Cannot sort the TO field when viewing Sent folder?

Cannot sort the TO field when viewing Sent folder?

When viewing my Sent folder I need to sort by the TO field.  For what it's worth, I can sort the SUBJECT field and the SIZE field (which is useless, imo)...but what about the TO field?  Am I doing something wrong??  There is no little triangle that pops up next to the word "TO".   Help!  This is very an extremely important feature, I used to do this all the time in Outlook.