Blocking an email sending for a contact interrupts the communications linked to the Email channel for that contact. The contact becomes inadmissible to receive emails (for the project and the account). Depending on the configuration of the communication types, a contact can be placed on a kill list automatically when an email is flagged as unwanted (spam or junk) or when unsubscribing.
Block the Sendings
To start, go to the contact's profile, then, in the upper right, click on Block email sendings:*You will see the option in the list only if you have the permission to execute this delicate action.
The Email channel will be disabled (red X) for that contact:
Unblock the Sendings
In the upper right of the contact's profile, click Unblock email sendings:*You will see the option in the list only if you have the permission to execute this delicate action.
The Email channel will be unblocked and email sendings enabled for that contact.
The contact identified you as spam in the inbox?If you unblock the sending to a contact, but this contact identified you as spam, the messages will continue to get into the spam folder, which will negatively impact your sender's reputation. You must ask the contact to identify you as legitimate/not spam. The terms used are different depending on the inbox provider of the recipient (Gmail, Outlook, etc.).
Blocking the email sendings to a contact will add this contact to the kill file (both for the project and the account). On the other hand, unblocking the sendings will remove the contact from the kill file. To learn more, see the article on the kill file. That article also explains how to add/remove several contacts at the same time (manually or by import).