In most cases, with marketing emails, senders must get permission from their contacts before sending any marketing campaigns to them. Around the world, many countries and regions require this by law.

Whenever a contact fills out a signup form and selects a check box agreeing to receive marketing communications, it's called an opt-in. Meaning the contact has opted-in to receive marketing communications from you.

We currently recognise four email opt-in types:

When you bulk import or individually add contacts to your lists, these contacts have an unknown email opt-in type by default. If contacts have an unknown email opt-in type, it's your responsibility to make sure that you can legally hold their details. This opt-in type means that we don't know how you obtained this email address or if the contact willingly opted into your campaigns.

Although our Data Watchdog checks that your lists are clear from problematic email data, it's your responsibility to make sure that you send emails only to contacts who've opted in.

If you send emails to contacts who haven't opted-in, you‘re likely to get complaints from anti-spam authorities, and they might add you to their block list. Block listing affects the sending reputation and deliverability rates of both your organisation, and Dotdigital.

Single opt-in is very simple. A contact provides their email address using your signup form, selects submit, and their contact information saves in your account. It's quick and straightforward, but there are a few problems.

With single opt-in, anyone could sign up on behalf of someone else. And there is no process to prove the contact is consenting, or that the email address is for a valid, monitored inbox. For these reasons, we don't recommend you use single opt-in.

Whether intentional or not, if you send emails to contacts who haven't fully consented to marketing communications, you‘re likely to get complaints from anti-spam authorities, and they might add you to their block list. Block listing affects both your and our reputation and deliverability rates.

Double opt-in always starts with a single-opt in. However, after signup, you are responsible for sending a confirmation email to the contact and storing a record of their opt-in consent.

We don't hold the record of consent for you for double opt-ins, so you must have it available in case the contact contests their consent in the future.

You must not change a contact's opt-in type to double opt-in without first getting and storing the contact's consent.

Verified double opt-in always starts with a single-opt in, but we add an extra step to ensure the contact is precisely who they say they are. After your contact opts in, we send a confirmation email to confirm it's them.

After a contact confirms their email address, you have the peace of mind that your contact is consenting with a valid and monitored inbox.

Not only do we recommend using double opt-in, but in many cases, you may be legally obliged to use it.

If you change the email opt-in type to Verified double for contacts already in your lists, we remove their email address from all of your lists until they click the confirmation link in the email we send them.

Opt-in types can show you how engaged your contacts are.

For example, contacts with a Verified double opt-in type are more likely to be interested in receiving your email campaigns because they've taken the time to opt-in and confirm their signup.

Verified double opt-in is the best practice for adding email addresses to your lists. If you receive any unfair spam complaints, Verified double opt-in gives you proof that a contact opted in – we keep this proof in our records.

If contacts complain or query their subscription and opt-in type, you can go to their Single customer view to find their last Subscribed date as well as their Opt-in type.