The author discusses how Postmark, an email service provider, needs to increase its capacity to handle growing demand. The current system has limitations due to physical constraints, such as the capacity of direct connect (DC) connections and load balancers. To address this, the team upgraded their DC connections from 1Gbps to 10Gbps links, which improved performance but still had limitations due to other parts of the system, including firewalls with limited bandwidth. The author is now exploring new solutions, such as upgrading firewalls, to further improve capacity and performance. Despite these challenges, Postmark has seen significant growth in email volume and customer support, and the team is committed to delivering fast and reliable email services.