add a bit about dealing with blocklists

service/email.md

@@ -503,6 +503,17 @@ run the timer by hand:
 Note that the normal value is `1`, not `0`, as the script counts
 `/var/mail` itself as a file.
 
+## Deal with blocklists
+
+Sometimes we end up on blocklists. That always sucks. What to do depends on
+who's blocking. Sometimes there'll be a contact address in the bounce message.
+Let's try to collect our experiences per provider here:
+
+### Microsoft
+
+You can request delisting here: https://olcsupport.office.com/ , you need a microsoft account to do so.
+They should get back to you soon to resolve the situation, if needed you can contact them on outlooksupport@microsoftsupport.com
+
 ## Disaster recovery
 
 N/A. The server should be rebuildable from scratch using the Puppet