Whenever I use icloud.com for email I have a problem with autofill. For instance, whenever I try to email my wife autofill/autocomplete suggests every conceivable permutation of email addresses that have been sent to her. If I type her name, it includes every email address she has ever had PLUS every combination of her address plus other people I sent in a group email. The default email address is to her and a real estate agent from 3 years ago! Also troubling is that email addresses from an old job continue to pop up. If I'm trying to email a person named "Todd" an email it will immediately pull up "Todd" from my old company. If I'm not careful I could be sending email to the wrong people constantly.
How do you fix this specifically for icloud.com?
In Mail check the Window Menu>Previous Recipients - you may find these unwanted email addresses listed there. There is a button to remove all those you don't need (likely most of them).