I have always been under the impression that the order of email addresses for a contact is the order in which their autocomplete suggestions will pop up. So if I have a contact with multiple email address and type their name into the
To: field, the order of the email address listed in the auto complete pop up will be the order in their contact info, and in particular by hitting tab it will auto fill the first email address of the contact info.
Recently, I've noticed that this is not the case sometimes. In particular I have two contacts that recently changed their main email address and Gmail does not want to update the autocomplete popup with the order I expect. Whether this is because it is no recognizing that the "first" email address in the contact info has changed or because perhaps the auto complete order is based on something else (such as the email address with the most volume associated with it), I do not know.
Does anyone know how to have this behave the way I'd like?
An answer mentioned removing the offending email address that's been previously the most emailed address, saving, then readding, and saving the contact again. This seems to work temporarily, but reverts within 6-8 hours.