
There are 2 different sets of steps that should be performed to resolve this:

The issue is not seen when the same user is sending mails from Kerio Connect Webmail or from any other computer. The error seen in Outlook's Send/Receive > Show Progress dialog is Error (0x80048002) while executing the task "Kerio Connect (KOC Offline Edition) - Messages are sent: The task was aborted before completion. If unsure about the steps to perform or would like Real World Technology Solutions support team members to assist and perform - please submit a support request for remote support session.When sending emails from the Microsoft Outlook client using the Kerio Connect email, the mails remain in the Outbox. Be sure to include as much detail as possible about Outlook's issue including if the issue consistently occurs, the times the issues tend to occur, the size of your mailbox and information about your internet connection and usage. If you continue to experience issues with Outlook, please submit a support request for Real World Technology Solutions support team to investigate further. Click it to connect (the button turns white) and click Send All. Click Send/Receive and look at the Work Offline button.

Note: Messages also get stuck in the Outbox when you click Send but you’re not connected.

If Outlook is closed or a device starts sleep mode while large email messages are being uploaded, additional issues with syncing messages can develop. When a message gets stuck in your Outbox, the most likely cause is one or many emails that contain large attachments trying to upload to Exchange Online mail services.
