After enabling 'Send To' integration in Attach Plus, the setting is somehow being turned off.
Basically, what is happening is that the following registry key is getting reset: HKEY_LOCAL_MACHINE\SOFTWARE\Clients\Mail.
If the (Default) value is "AttachPlus", then 'Send To' integration is turned on. If the (Default) value is "Microsoft Outlook", then 'Send To' integration is not turned on. We've seen Outlook reset this key when it is updated, but not under normal circumstances.
If you find that this setting is being reset, we'd be interested to know the cause.