The key lies in setting the appropriate options.

InOutlook Options, selectAdvanced.

Go to theSend and Receivesection.

Screenshot of Outlook Options

Select theSend immediately when connectedcheckbox.

What Happens When ‘Send immediately when connected’ Is Enabled?

In that case, it attempts delivery periodically thereafter.

Screenshot showing Advanced tab

If you are connected and Outlook is set toWork Offline, Outlook will not deliver the email.

The message is kept inOutboxuntil you set Outlook toWork Online.

The message is kept inOutbox.

Screenshot of Send and Receive in Outlook Options

Outlook attempts to deliver the email a few minutes after you have connected.

If you are not connected and Outlook is set toWork Offline, Outlook will not deliver the message immediately.