Editing Outlook Express (section)

===Extensibility===
Outlook Express does not have a documented [[object model]] like Microsoft Outlook. Programmatic access to, or control of Outlook Express for custom messaging applications or plugins is not officially documented or supported by Microsoft.<ref>{{cite web|url=http://support.microsoft.com/kb/239576 |title=Developer Support Limitations with Outlook Express |website=Support |publisher=[[Microsoft]] |date=June 25, 2006 |access-date=December 17, 2012|url-status=dead|archive-url=https://web.archive.org/web/20061029080705/http://support.microsoft.com/kb/239576|archive-date=October 29, 2006}}</ref> <code>IStoreNamespace</code> and <code>IStoreFolder</code> interfaces<ref>{{cite web|url=http://msdn.microsoft.com/en-us/library/ms710214.aspx |title=IStoreNamespace Interface |work=[[MSDN]] |publisher=[[Microsoft]] |date=2011-06-30 |access-date=2012-12-17}}</ref> were documented in 2003, but they are only related to the storage.

Some companies have managed to create their plugins hacking the interface using Windows [[Hooking|hooks]]. A significant one was the [[Pretty Good Privacy|PGP]] plugin because it was the only example of a working plugin whose [[source code]] was available (licensed under [[GPL]]). By 2003, some companies provided commercial solutions to develop add-ins.<ref>{{cite web|url=http://www.nektra.com/products/oeapi-windows-mail-outlook-express-plugin/ |title=Outlook Express API |publisher=Nektra |access-date=2012-12-17}}</ref>