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AgentiSend vs Postmark
Yes, for transactional email an agent sends through an API. A Free plan that does not expire: 1,000 emails a month, 100 a day, 3 domains, no card. Then plans from $9 a month (Starter, 30,000 emails). No plan daily cap; delivery paced per inbox provider. Or 20% off paid yearly. It is not a replacement for a product that is ahead on the rows marked in the other column.
Pick Postmark when you want 45 days of message history on the $15 plan, inbound mail on Pro, or a dedicated IP with a published price; pick AgentiSend when an agent holds the key and you want a send budget and a kill switch. The figures below are from Postmark pages fetched on 28 September 2026 and from this product's pricing table and published API.
Moving across? How a migration from Postmark actually goes.
| What matters | AgentiSend | Postmark |
|---|---|---|
| Trying it before paying | A Free plan that does not expire: 1,000 emails a month, 100 a day, 3 domains, no card. Then plans from $9 a month (Starter, 30,000 emails). No plan daily cap; delivery paced per inbox provider. Or 20% off paid yearly. | The developer plan is 100 emails a month and does not expire. There is no plan between that and 10,000 a month. |
| Price at 10,000 emails a month | $9 a month on Starter, which covers 30,000 emails, so $0.30 per 1,000 at the inclusion. | Basic is $15 a month for 10,000 emails, then $1.80 per 1,000. Pro is $16.50 with inbound. Platform is $18. |
| A spending limit per key | Every key is created with a send budget. The send path refuses with agent_budget_exceeded when it is spent, and a key cannot raise its own. The plan inclusion is a second ceiling (plan_limit_reached). | A per-key send budget is not on the pricing page. API permission controls are listed as a feature. |
| A retry never sends twice | Idempotency-Key is accepted on every endpoint that changes something and remembered for 7 days. | Postmark does not support an idempotency key. The support article says to detect duplicates yourself. |
| What a refusal tells you | Every refused request carries code, message, fix (the call that repairs it), docs_url and retryable. | A fix field naming the next call is not on the idempotency article or the webhooks overview. |
| How long the log keeps a message | 7 days on Free, 30 on Starter, 90 on Pro, 180 on Scale. It is part of the plan and there is no add-on to buy. | 45 days of activity on every listed plan. Pro and Platform can buy custom retention from 7 to 365 days. |
| Receiving mail | No inbox object and no inbound mail yet; AgentiSend receives only bounces and complaint reports for mail it sent. | Inbound email processing is on Pro and Platform. The pricing table marks it absent on Free and Basic. |
| Signed webhooks | Signed HTTP webhooks. POST /webhooks/{id}/replay re-sends a range you name, and a delivery that ran out of retries is listed as dead_lettered. | Postmark does not support HMAC webhook signatures. The overview recommends HTTP basic authentication plus an IP allow list. |
| A dedicated address | Dedicated IP on request. Once one is assigned, the published ramp is 20% of volume to day 7, 40% to day 14, 60% to day 21, 80% to day 28, then all of it, on GET /dedicated-ips/ramp. | Dedicated IPs start at $50 a month, for customers sending 300,000 emails a month or more, on Pro or higher. |
Sources
- Trying it before paying. Ours: the published API, /pricing and /security. Theirs: https://postmarkapp.com/pricing (captured 2026-09-28).
- Price at 10,000 emails a month. Ours: the published API, /pricing and /security. Theirs: https://postmarkapp.com/pricing (captured 2026-09-28).
- A spending limit per key. Ours: the published API, /pricing and /security. Theirs: https://postmarkapp.com/pricing (captured 2026-09-28).
- A retry never sends twice. Ours: the published API, /pricing and /security. Theirs: https://postmarkapp.com/support/article/what-is-an-idempotency-key (captured 2026-09-28).
- What a refusal tells you. Ours: the published API, /pricing and /security. Theirs: https://postmarkapp.com/support/article/what-is-an-idempotency-key (captured 2026-09-28).
- How long the log keeps a message. Ours: the published API, /pricing and /security. Theirs: https://postmarkapp.com/pricing (captured 2026-09-28).
- Receiving mail. Ours: the published API, /pricing and /security. Theirs: https://postmarkapp.com/pricing (captured 2026-09-28).
- Signed webhooks. Ours: the published API, /pricing and /security. Theirs: https://postmarkapp.com/developer/webhooks/webhooks-overview (captured 2026-09-28).
- A dedicated address. Ours: the published API, /pricing and /security. Theirs: https://postmarkapp.com/pricing (captured 2026-09-28).