Emailing results requires email delivery (any paid tier, from $5). On the free tier, publish the results and share the public link yourself.
Publish first
Email results to voters only becomes available after you've published a public results link with Publish results — see Publishing results & receipt verification. Results need to be public before anyone can be pointed to them.
Sending it
Once published, click Email results to voters on the closed election's page. This is a one-shot action: it sends one email to your voter roster and can't be run twice for the same election, so there's no risk of results going out to the same people repeatedly.
Who's excluded
The send automatically skips voters whose invitation bounced and voters who unsubscribed from emails — the same exclusions used for reminders — so you're not sending to addresses that already failed or people who opted out.
What the email contains
The email links to the same public results page anyone can already reach without signing in — the unguessable link created when you published. It doesn't include a voter's individual receipt code; voters who want to verify their own ballot was counted do that by searching the published receipt list themselves, using the code they were shown when they voted. See Publishing results & receipt verification.