This is a common problem with the MS Outlook Email VBO. The VBO is much more stable than MAPIEx, but it appears that it comes with its own set of issues.
Some organizations start Outlook up in order to ensure the emails don't get stuck in drafts/outbox. I guess the instance of Outlook must be closing too quickly before the email is sent sometimes.
In my opinion, the right way to solve the problem is to not use Outlook (the desktop app) to send emails. There are a couple of options. The easiest is SMTP. If your organization doesn't allow using SMTP, then you could also consider Graph API if you have someone who knows how to configure it and make calls to it.
I suppose there may also be a code solution to the problem by having it check the outbox and drafts folder when sending emails to ensure that the invisible instance of outlook isn't closed too quickly. But I never went that route.
Edit: I should also mention that the Agilify EWS object on the Digital Exchange is another good option for solving the issue. You should be able to do this without any coding and without needing more permissions. But note that the object is not perfect. In my opinion though, it's much better than sending with the MS Outlook Email VBO.
https://digitalexchange.blueprism.com/dx/entry/16835/solution/ms-exchange-functions---agilify------------------------------
Dave Morris
3Ci @ Southern Company
Atlanta, GA
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Dave Morris, 3Ci at Southern Company