diff --git a/docs/curl.1 b/docs/curl.1
index 30c18763a..ebacfa243 100644
--- a/docs/curl.1
+++ b/docs/curl.1
@@ -1627,6 +1627,19 @@ The user name and passwords are split up on the first colon, which makes it
 impossible to use a colon in the user name with this option. The password can,
 still.
 
+When using Kerberos V5 with a Windows based server you should include the
+Windows domain name in the user name, in order for the server to succesfully
+obtain a Kerberos Ticket. If you don't then the initial authentication
+handshake may fail.
+
+When using NTLM, the user name can be specified simply as the user name,
+without the domain, if there is a single domain and forest in your setup
+for example.
+
+To specify the domain name use either Down-Level Logon Name or UPN (User
+Principal Name) formats. For example, EXAMPLE\user and user@example.com
+respectively.
+
 If you use a Windows SSPI-enabled curl binary and perform Kerberos V5,
 Negotiate or NTLM authentication then you can tell curl to select the user
 name and password from your environment by specifying a single colon with this