added instructions for testing

linux/mail/msmtp.md

@@ -32,3 +32,13 @@ since you will be putting a plaintext password in this config file, make sure it
 ```
 chmod og-r /etc/msmtprc
 ```
+
+## test
+you can test if you can connect to the server by running:
+```
+msmtp -Sd
+```
+or try sending yourself an email by running:
+```
+echo "this is a test" | mail -s "testing" youremail@yourdomain
+```