Inbound Usage and Rate Limits
Inbound Usage and Rate Limits
Postscale uses one shared monthly email quota for sending and receiving. Outbound usage is counted per accepted recipient, including To, Cc, and Bcc. Inbound usage is counted per accepted inbound message. On Free, the monthly allowance is a hard cap: once it is exhausted, new inbound messages are failed permanently instead of being held for retry. Published plan throughput, account review status, and abuse-prevention controls still apply. To protect all customers, Postscale can temporarily defer inbound messages when an account exceeds current operational limits.
Shared Plan Quota
Your monthly plan allowance is shared across outbound and inbound email:
| Direction | What counts |
|---|---|
| Outbound API/SMTP | One unit per accepted recipient across To, Cc, and Bcc |
| Inbound processing | One unit per accepted inbound message |
Messages rejected before Postscale stores or dispatches them do not consume quota. Temporary throughput deferrals also do not consume quota unless a later retry is accepted.
Inbound processing is available on every plan. Accounts get access to:
- Email parsing and JSON webhook delivery
- Attachment handling and storage
- Forwarding rules and catch-all addresses
- DMARC report collection
- Masked email aliases (Shield)
Quota, throughput, retention, and abuse-prevention limits vary by plan and account status. Check the pricing page or dashboard for the current limit attached to your account.
Limit Model
| Limit type | How it works |
|---|---|
| Shared monthly quota | Applied per organization across accepted outbound recipients and accepted inbound messages |
| Free monthly quota | Hard cap. Once exhausted, inbound messages are failed permanently so senders stop retrying |
| Paid monthly quota and overage | Paid plans continue accepting eligible inbound messages and apply the shared usage and overage rules for the plan |
| Plan throughput | Applied per organization according to the active plan and account status |
| Burst handling | Evaluated over rolling windows so short bursts can be accepted when capacity remains |
| Abuse controls | May reduce or pause processing for suspicious traffic patterns |
| Custom volume | Available by agreement for workloads that exceed published plan limits |
Throughput limits are operational controls. Monthly quota and any paid overage use the shared send + receive email count.
What Happens When You Hit the Limit
When a Free organization exhausts its shared monthly quota, Postscale fails additional inbound messages permanently. This prevents retry loops and keeps the sender's mail server from repeatedly redelivering messages that cannot be accepted under the current plan.
When your organization exceeds its current inbound throughput limit, Postscale responds with a temporary SMTP deferral. The sending mail server is asked to retry later, which is standard SMTP behavior.
This means:
- Standards-compliant senders retry. The sender's mail server usually holds the message and tries again.
- Postscale does not issue an immediate permanent rejection for ordinary throughput deferrals.
- Delivery resumes automatically once the account is back under its limit.
Most senders retry temporary deferrals within minutes, though retry behavior is ultimately controlled by the sender's mail server. This approach protects your account and Postscale infrastructure without accepting more traffic than the account can process.
Short bursts are expected. Keep sustained traffic within your published plan limits, and contact support before large migrations or backfills.
How This Compares
Email platforms account for inbound in different ways. Here's how Postscale stacks up:
| Feature | Postscale | SendGrid | Mailgun | Postmark |
|---|---|---|---|---|
| Inbound pricing | Shared send + receive quota | Paid add-on | Per email | Shared monthly email volume |
| Free tier | Evaluation volume | — | Limited | — |
| Webhooks | Yes | Yes | Yes | Yes |
| Attachments | Yes | Yes | Yes | Yes |
| DMARC reports | Yes | — | — | — |
| Masked aliases | Yes | — | — | — |
Postscale bundles inbound processing, webhook delivery, DMARC reporting, and masked aliases into one product surface and one shared email allowance.
Designed for Real Workloads
The limits are designed for normal product workloads:
- SaaS support inboxes — Most teams fit comfortably within the published shared quota and throughput limits
- Notification processing — Parse bounce notifications, auto-replies, and out-of-office messages within the same shared quota model
- Email-based workflows — Build ticket systems, CRM integrations, or approval workflows without a separate inbound quota model
- IoT and alerts — Receive machine-generated emails from monitoring systems and sensors
If your application regularly approaches the limit, upgrading your plan or arranging custom throughput increases capacity without changing your MX integration.
Data Retention
Inbound emails are stored for 90 days, giving you time to process, review, and debug. Postscale stores parsed headers, bodies, and attachment metadata; the original raw MIME source is not retained by default. Attachments are stored separately in Postscale-managed object storage and are cleaned up with inbound email retention unless a shorter lifecycle policy applies. Where application-side attachment encryption is enabled, attachment objects are encrypted before object storage upload and decrypted only through authenticated Postscale download endpoints.
After the retention period, data is automatically cleaned up to keep your account tidy and your database performant.
If your workload exceeds the Scale plan limits, contact us to discuss custom throughput for your organization.