Netmail Archive 6.x
Outlook will try to protect the user experience by disabling add-ins that it considers to be misbehaving. When the Netmail add-in is loaded it needs to contact a URL, download settings, perform authentication, etc... and in some environments this process could take longer than Outlook is willing to wait. Consequently Outlook will disable the add-in via a registry key so next time the start-up is quicker. Outlook will not attempt to reload it unless the registry key is manually changed back or the add-in is completely re-installed.
The following steps will help you determine if an add-in has been disabled, and how to re-enable it:
1) Click on the Windows Start button, and run regedit.exe
2) Open the following key in the registry:
where (name_of_the_addin) is usually something similar to: M+ArchiveOutlookAddin.
3) In the right portion of the screen, you should see the values stored in this key. One of the values is "LoadBehavior". If the value of this key is 2, then the add-in is disabled. You will need to set the value to 3 to re-enable it, and then restart Outlook.
Uninstalling and re-installing the add-in will also fix this issue temporarily, but it won't prevent it from reoccurring. To permanently exclude the add-in from this check at start-up, follow the procedure recommended by Microsoft here: https://blogs.msdn.microsoft.com/emeamsgdev/2017/08/02/outlooks-slow-add-ins-resiliency-logic-and-how-to-always-enable-slow-add-ins/