No. The IP address in your SPF (Sender Policy Framework) record should remain as the IP address of the server that hosts your iMIS site. Do not change this to the WAF IP address.
A Sender Policy Framework (SPF) record is a type of Domain Name Service (DNS) TXT record that identifies which mail servers are permitted to send email on behalf of your hosted website domain. The purpose of an SPF record is to detect and prevent spammers from sending messages with forged "From" addresses on your domain.
Confirmation emails, password reset emails, and emails sent from the iMIS Communication Suite are sent via SMTP on your iMIS server. Since the IP address of your iMIS server is *not* changing, and emails will continue to be sent from that IP address -- you should not change this entry.