Implementing Proofpoint, changing MX records, and undergoing IP warming are all significant infrastructure changes that can impact email deliverability. Gradual IP warming is crucial for establishing a positive sending reputation, and any sudden spikes in email volume can trigger spam filters. DNS changes, especially MX records, require time to propagate, leading to potential temporary delivery failures. Proper setup and maintenance of DKIM, SPF, and DMARC are critical, and changes to the email infrastructure may necessitate updates to these records. It is essential to monitor key metrics like bounce rates, engagement, inbox placement, and spam complaints to identify and address deliverability issues. Sender reputation is paramount, necessitating careful list management and avoidance of spam-like practices. Utilizing subdomains for different mail streams is beneficial for managing reputation, especially with Gmail.