Solution

The GFI Engineering team has investigated this behavior, and they concluded that the issue stems from how Outlook is processing aliases, and in cases where there is a large number of aliases, the above error is encountered.

The multiple tasks you're seeing in Outlook are due to how the MAPI (Messaging Application Programming Interface) service handles different email sender addresses. Here's what's happening:

• For each FROM address (email alias) you use, Outlook needs to create a separate transport provider in the KOFF MAPI service
• Each transport provider has both send and receive capabilities
• This architecture results in Outlook showing multiple tasks per transport provider
• The task ordering is handled internally by Outlook, with no option to control it

While performance profiling of the MAPI providers and KoffBackend.exe showed no significant bottlenecks, there is a workaround to reduce the queue length. You can modify the Send/Receive group settings in Outlook. Follow these steps to resolve the issue of emails getting stuck in the Outbox:

1. Modify Send/Receive Group Settings:
   • Open Outlook and navigate to File → Options → Advanced → Send/Receive.
   • Edit the "All Accounts" group.
     
   • Enable "Include the selected account in this group" only for your primary account.
     
   • Disable this option for secondary/alias accounts.
     
2. Expected Outcome:
   • Only one task will be created when using "Send/Receive All".
   • When sending from an alias, only the specific account will be used.

Important Note: The Send/Receive groups are stored in .SRS files used internally by Outlook. Microsoft does not provide documentation for these files, so manual adjustments are limited to the above steps.