Learn how to send emails when you lack internet connectivity.
To send emails while offline, you will need to manually send emails drafted while offline upon regaining internet connectivity.
Normally, when you send an email in Outlook while lacking internet connectivity, your email is queued in Outlook's Outbox feature. Once you regain internet connectivity, your email is automatically sent.
With Outlook Add-Ins like Preava Prevent, the Outbox feature unavailable as emails must be scanned by Preava's servers before they can be sent (or queued to be sent in the Outbox).