Hi, An.

Usually, contacts that have no email address are contacts that report via phone, Facebook and Twitter.

As for the contacts that only have a phone number, there is no destination for the message that you add to be sent to the customer, (you cannot write a text message to a phone number) and hence the reply button would be hidden for tickets raised for the contact.

Facebook and Twitter tickets can be replied on the same ticket since the ticket would have the reference to the post or the DM or the tweet from which the ticket was initially raised. However, if you create a new ticket for a Facebook or a Twitter contact, you cannot reply to these contacts since they do not have any reference of a DM or a post for you to reply to them and hence the reply button would be hidden again.

I hope this gives you more insight. Do write to support@freshdesk.com if you want more information on this.

Happy supporting!