How do I restore auto function filling in addresses on emails?

Please clarify. that feature has been a default for 20 years, so I am unclear on your request. thank you

Yes... it has worked on my computer(s) for years too. But now, when I start typing an address to send someone an email it stays blank. I looked for a setting that I might have inadvertently turned off - but no luck. I have to go through old emails to find their listing.