diff --git a/src/calibre/utils/smtp.py b/src/calibre/utils/smtp.py
index b716099f5b..68dfdde3c9 100644
--- a/src/calibre/utils/smtp.py
+++ b/src/calibre/utils/smtp.py
@@ -34,7 +34,13 @@ def safe_localhost():
     # RFC 2821 says we should use the fqdn in the EHLO/HELO verb, and
     # if that can't be calculated, that we should use a domain literal
     # instead (essentially an encoded IP address like [A.B.C.D]).
-    fqdn = decode_fqdn(socket.getfqdn())
+    try:
+        fqdn = decode_fqdn(socket.getfqdn())
+    except UnicodeDecodeError:
+        if not iswindows:
+            raise
+        from calibre_extensions.winutil import get_computer_name
+        fqdn = get_computer_name()
     if '.' in fqdn and fqdn != '.':
         # Some mail servers have problems with non-ascii local hostnames, see
         # https://bugs.launchpad.net/bugs/1256549