diff --git a/admin-guide/configuration/icinga2.md b/admin-guide/configuration/icinga2.md
index 8ca37a47..490569c2 100644
--- a/admin-guide/configuration/icinga2.md
+++ b/admin-guide/configuration/icinga2.md
@@ -99,6 +99,8 @@ This can be configured in Hiera with the `icinga2::alerting::severity` key which
 | `4`           | e-mail           | office hours |
 | `5`           | no notifications | never        |
 
+(Currently `3` and `4` behave the same.)
+
 Please note that services where the `criticality` variable is set then time when notifications are sent out is also restricted:
 
 | service criticality | time         |
@@ -110,6 +112,7 @@ Please note that services where the `criticality` variable is set then time when
 
 The minimal settings are applied, e.g. a service with criticality `C` will never cause a notificiation independent of the node severity.
 
+To receive notification messages over SMS, you need to register your mobile phone with Icinga2. You may request this informing icinga2-support@psi.ch about your wish. Alternatively you will get an e-mail with the request to do so when the first SMS was supposed to be sent out for you and the phone number is still missing.
 
 ## Default Checks