chore: Enable email channel (#1851)

spec/mailers/conversation_reply_mailer_spec.rb

@@ -95,7 +95,7 @@ RSpec.describe ConversationReplyMailer, type: :mailer do
       let(:conversation) { create(:conversation, assignee: agent, inbox: inbox_member.inbox, account: account) }
       let!(:message) { create(:message, conversation: conversation, account: account) }
       let(:mail) { described_class.reply_with_summary(message.conversation, Time.zone.now).deliver_now }
-      let(:domain) { account.domain || ENV.fetch('MAILER_INBOUND_EMAIL_DOMAIN', false) }
+      let(:domain) { account.inbound_email_domain }
 
       it 'renders the receiver email' do
         expect(mail.to).to eq([message&.conversation&.contact&.email])