2 of 2 people found this helpful
I cannot answer the "why" question, but thought this feedback MIGHT be helpful...
Specifically where is your "focus" at the moment, over to the left in the mail folders pane? Are you looking at an email account under the Online section?
If so, what you describe has been this way as long as I can remember (going back to version 3.2 back in 1997), INCLUDING being that way in version 2015.2, today.
However, just now, in version 2015.2, with my focus just about anywhere else (e.g. Inbox, Outbox, Deleted, Filed, Sent, etc.), then Edit E-Mail Options is NOT grayed out and IS available.
Hope this feedback helps.