REACH emails being sent to junk mail suddenly

REACH emails being sent to junk mail suddenly

It was noticed today that all of the pastoral/duty reports sent out to staff on their education department email addresses have been sent to their junk files.
It has only started today and as there have been no changes made to any of our accounts, it is a bit of a mystery as to why it is happening.
I have been able to 'create rules' in my outlook to hopefully stop it from happening again, but not all of our staff are tech savvy and will miss important emails because of this.
Is there a way to change it from the REACH side of things to prevent it from happening? The change logs don't specifically show any changes to settings for emails, but something in the changes made on the 13th may have triggered something unexpected.

Thanks in advance for any help you can offer

Niamh