--- a/sylpheed/libsylph/ssl.c	
+++ a/sylpheed/libsylph/ssl.c	
@@ -121,6 +121,8 @@ void ssl_init(void)
 		certs_file = find_certs_file("/etc/ssl");
 		if (!certs_file)
 			certs_file = find_certs_file("/etc");
+		if (!certs_file)
+			certs_file = find_certs_file("/usr/share/ca-certificates");
 #endif
 	}