⚡ Wire Capacity & MTA Sizing

SMTP Throughput & Concurrency Sizing Calculator

Calculate required outbound concurrency, connection reuse, and wire latency to meet dispatch deadlines.

Campaign Batch Size 250,000
Target Delivery Window (Hours) 2.0 Hours
Average Latency per Email (ms) 120 ms
Msgs per TCP Connection (Pipelining) 10
Required Velocity
34.7 / s
125,000 / hr
Concurrent Sockets
5
Parallel connections
Recommended MTA Threads
15
3x safety headroom
Egress Bandwidth
13.9 Mbps
Estimated network load
AUTO-CALIBRATED MTA CONFIGURATION pmta.conf 
max-smtp-out 15
max-msg-per-connection 10
smtp-pattern-list standard-backoff
⏱️ Delivery Window vs. Socket Concurrency Matrix
Dispatch Target Time Delivery Velocity (msgs/sec) Required Sockets Safety Thread Cap ISP Throttle Rating

🚀 Need 1M+ Emails Dispatched in Under 60 Minutes?

AutoSMTP provisions tuned high-IOPS bare-metal instances delivering sustained speeds exceeding 250,000 emails per hour per node.

The Physics of High-Volume SMTP Throughput

SMTP is fundamentally an interactive network protocol governed by round-trip network time (RTT). Every single outbound email delivery requires TCP 3-way handshakes, TLS 1.3 cryptographic negotiation, EHLO announcements, MAIL FROM commands, RCPT TO checks, and DATA transfers.

Throughput is mathematically bound by Little’s Law: Throughput = Concurrency / Latency. Increasing dispatch velocity without proper connection pipelining or by overwhelming recipient MX rate limits triggers 421 4.7.0 and 451 4.7.650 temporary deferrals. AutoSMTP calibrates connection pools to maintain optimal queue velocity without breaching ISP concurrency ceilings.