Problem with distribution list

I created a distribution list with 55 email addresses. I want to add or edit an address. When I click on the distribution list, I see this.

Here’s my list with the (hidden) email addresses. When I try to send a message to my list, it’s no longer visible.



Who’s your contacts provider please?

That’s to say ?

In other words, which account you have your contacts under (Exchange, Fastmail, …)

When I create a contact, there’s no check on a contact provider. I create the contact directly in the Em client. For example, I just created a contact, [email protected]. There was no check to see if this address even existed.