Our organization uses Office 365 for our primary domain Email addresses. Let's call this domain ourdomain.com
However, due to the daily outbound message limit imposed by 365, we've set up in-house Exchange 2003 server to handle our statement emails to our customers. These Emails are sent from ourdomain.net
But we notice some Email messages (sent from in-house ourdomain.net
addresses) are bouncing back because of invalid SPF record and reverse DNS mismatch.
Reverse DNS for the IP belonging to ourdomain.net
currently still returns mail.ourdomain.com.
This is because prior to switching over to 365, we were using our in-house Exchange server for mail services for our primary domain ourdomain.com
I know I can call our ISP and have this updated and I'm pretty sure that this won't affect 365.
But my main concerns or question is with what should the SPF records read for both ourdomain.com
domains to ensure that:
Our In-house Exchange server can send Emails using ourdomain.com and ourdomain.net Email addresses without being flagged
Emails sent to and from ourdomain.com (365) are not affected in any way
Can you help me with some recommendation?