Postmark recently experienced two major maintenance windows, resulting in significant delays for time-sensitive emails, due to a planned but imperfect upgrade process. The company had invested in new hardware and networking infrastructure, which has allowed for more control over growth and performance, but the migration to new firewalls was complicated, requiring multiple attempts. Despite the challenges, Postmark aims to finalize the process by January 4th, with the goal of minimizing downtime to 15 minutes or less, and is working towards zero-downtime maintenance windows in the future.