Typing a part of the email address string other than the beginning of the string does NOT work, I kindly urge Zoho to fix this.

Let's say you remember writing an email so someone called "smith" from company "corp.com", but can't remember their first name, typing "smith" or "corp.com" will NOT show the email you are looking for, only if you start typing the beginning of the email address string, e.g. "adam", the email will be suggested for auto-completion.

I would argue this is a BUG, not a feature!