Fix #9923: mailcap now uses the OS path separator for the MAILCAP envvar. Not backported, since it could break cases where people worked around the old POSIX-specific behaviour on non-POSIX platforms.
diff --git a/Misc/NEWS b/Misc/NEWS
index c0fa159..85dbe25 100644
--- a/Misc/NEWS
+++ b/Misc/NEWS
@@ -268,6 +268,9 @@
 Library
 -------
 
+- Issue #9923: The mailcap module now correctly uses the platform path
+  separator for the MAILCAP environment variable on non-POSIX platforms.
+
 - Issue #12835: Follow up to #6560 that unconditionally prevents use of the
   unencrypted sendmsg/recvmsg APIs on SSL wrapped sockets. Patch by David
   Watson.