82% less spend, zero deliverability hit.

Keelhaul replaced a five-figure-a-month Postmark contract with VoltMail Pro Max in a single weekend. Engineering, not procurement, made the call.

Email spend

−82%

first 30 days

Send volume

4.2M

monthly

Migration time

6 hrs

incl. DKIM rotation

Bounce rate

0.18%

down from 0.34%

“I scheduled a one-week migration sprint. We finished Saturday afternoon. The pricing page is literally the contract — no hidden overage math, no per-seat creep.
PR
Priya Ranganathan
Staff Engineer · Keelhaul

// the problem

Per-message billing was a moving target.

Keelhaul ships shipment events to 1.4M shippers. Postmark was charging $0.40 / 1k, and the price kept stepping up at every renewal. Worse, suppression lists were per-server, not per-account — meaning their three sending IPs each maintained an independent bounce list with drift between them.

Three sending IPs, three diverging suppression lists.
Renewal-time price hikes with no predictable schedule.
No webhook replay — outages meant manual SQL backfills.

// how voltmail fit

One contract, one suppression list, replayable webhooks.

On migration day Priya's team ran our CSV importer against the Postmark suppression export. 240k rows landed in the global blocklist within ninety seconds. They rotated DKIM keys with our dual-selector flow — zero downtime, zero bounce-rate spike. The webhook replay tool let them fan out 6 hours of missed events to their downstream after the cutover.

Global suppression list — single source of truth across all sending domains.
Dual-selector DKIM rotation — no mail server downtime.
Replay-able webhooks meant a clean cutover with zero lost events.

// six months later

They send 4.2M / month and it costs 82% less.

The Pro Max plan ($79 + overage) replaced $14k/mo of Postmark + an Amazon SES fallback. Bounce rate dropped 0.34% → 0.18% because the unified suppression list catches retries across domains. Inbox placement at Gmail climbed from 96.1% to 99.4%.

Total spend: $14,000/mo → $2,500/mo.
Gmail inbox placement: 96.1% → 99.4%.
On-call escalations from email-related incidents: 4 → 0 in last 90 days.

“My CFO sends me thank-you GIFs. My on-call rotation sends me silence. Both are wins.
PR
Priya Ranganathan
Staff Engineer · Keelhaul

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