If your leads display the notification, This Lead has chosen not to receive emails or may have an invalid address, but they have valid email addresses and have not opted to unsubscribe from any campaign you have submitted, this notification may be related to your Landing Page forms.
In the past, the Landing Page form had an option for the leads to choose whether or not they wanted to receive promotional emails from your company. This feature has been discontinued for automatic use, but you can still insert this field into forms (opt-in email).
When the opt-in field, I would like to receive promotional emails from the company is enabled on your Landing Page (created in the old template), you need to pay attention: If the lead does not click on the checkbox choosing to receive promotional emails, RD Station Marketing will record that the Lead doesn't want to receive emails, activating this notification.
You can create a segmentation to check how many and which leads chose not to receive your promotional emails:
Even if a lead has a valid email and hasn't unsubscribed from your base in any of the campaigns you sent, some may have opted not to receive your emails on the conversion form simply by not selecting your opt-in field.