Documentation/email-clients.txt: add info about Claws Mail

Claws Mail GUI client works.
The client is available at http://www.claws-mail.org

Signed-off-by: Richard Leitner <dev@g0hl1n.net>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>
diff --git a/Documentation/email-clients.txt b/Documentation/email-clients.txt
index 9af538be..eede608 100644
--- a/Documentation/email-clients.txt
+++ b/Documentation/email-clients.txt
@@ -77,6 +77,17 @@
 to insert into the message.
 
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+Claws Mail (GUI)
+
+Works. Some people use this successfully for patches.
+
+To insert a patch use Message->Insert File (CTRL+i) or an external editor.
+
+If the inserted patch has to be edited in the Claws composition window
+"Auto wrapping" in Configuration->Preferences->Compose->Wrapping should be
+disabled.
+
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 Evolution (GUI)
 
 Some people use this successfully for patches.