Welcome to the Community!
We'd like to learn more details of your concern. Are you using our Post Office or an email client such as Outlook?
If you are using Post Office, you may simply add the email address to your Contacts to activate the autofill and there are two ways for you to do this.
Adding Email address to your Contacts
If there is anything that we can lend a hand with from here, please always feel more than welcome to give us a shout!