With regulations like GDPR expanding our rights to privacy, it's important to have proper authorization from someone before sending business communications to them.
When using Insightly's Web to Lead or Web to Contact form, you can include an opt-in field for your web visitors. You'll need to create a custom opt-in field in Insightly and then include it when building your webform.
See How to create a Web to Contact or Web to Lead webform and How to create a custom field.