Emails sent from Access using Outlook are sent but left in outbox

[microbyte]

Hi,

Hoping someone can help.

Environment:


Exchange 2010
Office 2013
Outlook profile with 2 exchange accounts (one for the user, one is a generic account used by multiple users, this is set as the default account)

Scenario:
We have an access database that sends emails using outlook and send out using the default mailbox.
The emails send fine but the message is left in the Outbox.

If you sent an email from Outlook using the default account it works fine.

Has anyone experienced this before?
Any ideas on what to check/try?

Thanks
Will