diff --git a/content/nerdstuff/certificates.md b/content/nerdstuff/certificates.md
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+---
+title: Certificates 
+menu:
+  main:
+    parent: Nerdstuff
+---
+
+## Retrieve certificate information from server
+
+### HTTPS
+
+```
+openssl s_client -connect mail.br0tkasten.de:443 -servername mail.br0tkasten.de </dev/null 2>/dev/null | openssl x509 -noout -text
+```
+
+### IMAP with STARTTLS
+```
+openssl s_client -starttls imap -connect mail.br0tkasten.de:143 </dev/null 2>/dev/null | openssl x509 -noout -text
+```
+
+### SMTP with STARTTLS
+```
+openssl s_client -starttls smtp -connect mail.br0tkasten.de:587 </dev/null 2>/dev/null | openssl x509 -noout -text
+```