We have two schools. School 1 - A.com and School 2 - B.com
School 1 has an onsite Exchange 2013 server which is part of a Hybrid Office365 setup. School 2 is an accepted domain on the Office 365 setup but it's MX record points straight to Microsoft.
We have an MIS system with a connector using the Exchange server that can send out emails as anything i.e. AnyAddress@A.com
School 2 is now using the same MIS system. If I send an email to a B.com address from an A.com address it works fine. If however I change the From address to a B.com email address as the sender the email doesn't arrive and must be being rejected by the Exchange server. I tried adding in B.com as an accepted domain but it still didn't work.
Ideally we need School 2 - B.com to be able to send out email as themsevles to parents so that when the parents arrive the emails will end up back in their Office 365 accounts.
Is this possible or will SPF stop this sort of thing dead as I guess we're basically spoofing?
If it is possible what's the best way to achieve this without changing config records for Office 365, which as a Hybrid setup is complicated enough :)