Double opt-in: confirm the address before you send

How it works

1. A person enters their email address in a signup form.
2. The sender emails one message with a confirmation link.
3. The person clicks it, and only then joins the list. The time of the click is a record of consent.
4. If they never click, they never join.

With single opt-in there is no confirmation: submitting the form subscribes the person at once.

Why it matters

• Typos and fake addresses stay off the list. An address nobody can open never confirms, so it never hard-bounces later.
• Nobody is signed up by someone else. A bot, or a person typing a stranger's address, can fill in a form, but only the owner of the inbox can confirm.
• Gmail recommends it. Google's sender guidelines say to confirm each recipient's email address before subscribing them.
• The trade-off is growth. Some real people never click the confirmation, so the list grows more slowly.

How Mimeo handles it

Mimeo is built for opt-in lists. People arrive as events your site or app sends to Mimeo. The convention is an opted_in event, with the form named in details.entry_point (opt-in intake). That puts the confirmation step where the signup happens: if your site sends opted_in only after the person confirms, unconfirmed addresses never reach your list.

If you'd rather have Mimeo send the confirmation email, build it as a flow:

1. Trigger on your signup event.
2. Send the confirmation email.
3. A gate waits, with an expiry, until the person has clicked a link in that email. Mimeo's click conditions count human clicks only, so a link scanner can't confirm anyone.
4. On the Criteria met path, add a confirmed tag.

Start your welcome flow from that tag being added, and have your broadcast segments require it. People who never confirm stay outside every audience that requires the tag. See Mimeo terms for events, flows and gates in Mimeo's own words.