Some emails are placed in a "Quarantine" allowing users to release the emails themselves if they are from a trusted source, emails like this will look like this:

If you get these emails to your individual account (e.g. dcarpenter@crst.org.uk) you can follow this guide instead:
Helpdesk : Central Region Schools Trust (crst.org.uk) 

However the quarantined emails are going to a shared mailbox (e.g. finance@, office@ etc) then you will need to do the following:

Quick Actions:

Clicking on the Deliver, Allow List or Block List links will affect the email on the same line.

You will be taken to a login page with the email address pre-filled in for you, click Next:

On the next page click on the "Email a temporary passcode" link:

Head back to your shared mailbox and copy the passcode, paste it in the box above and click Log in:

If you clicked Allow for example, the email will now be released:

View all Quarantined Mail:

If you want to check all quarantined mail, click on the "Message Log" link in the quarantined email and follow the login steps above. Once logged in with a temporary passcode, you will see the following:

From here you can select the emails that have been quarantined and Deliver or add them to your Allow List using the buttons above.