Use outgoing_mail.fromAddress for alertmanager mails

ansible/roles/apps/templates/settings/prometheus-stack.yaml

@@ -16,7 +16,7 @@ alertmanager:
   config:
     {% if outgoing_mail.enabled %}
     global:
-      smtp_from: "alertmanager@{{ domain }}"
+      smtp_from: "{{ outgoing_mail.fromAddress }}"
       smtp_smarthost: "{{ outgoing_mail.smtp.host }}:{{ outgoing_mail.smtp.port }}"
       smtp_auth_username: "{{ outgoing_mail.smtp.user }}"
       smtp_auth_password: "{{ outgoing_mail.smtp.password }}"