What is Opt-in?
Opt-in is a user’s active consent to receive emails or other communication. In the EU, a valid opt-in is required for email marketing to consumers under the GDPR. Without an opt-in, sending commercial email to consumers is not legally allowed.
Single opt-in versus double opt-in
With single opt-in, someone is added to the list straight after signing up. With double opt-in, the subscriber receives a confirmation email and is only subscribed after clicking the confirmation link. Double opt-in gives you a cleaner list with higher engagement, but also more drop-off during sign-up.
Opt-in and the GDPR
For B2C email marketing, opt-in is mandatory: consent must be freely given, specific, informed and unambiguous. Always record when and how someone gave consent, for your own records.
Opt-in with lead magnets
Signing up for a lead magnet counts as an opt-in if it is clearly stated what the consent is for. Link it straight to a drip campaign for lead nurturing.
Should I always use double opt-in?
In the Netherlands it is not legally required for B2B, but it is strongly recommended for list quality and deliverability.
Can I use purchased email lists?
No. Purchased lists have no opt-in and breach the GDPR for B2C. More at developers.google.com/search.