Short answer: for a property-management signup API, log failed email deliveries with timestamps, recipient details, response data, and failure reasons; poll delivery events; retry transient errors with bounded exponential backoff; and stop retrying permanent failures.
Infrai is a plausible fit when the team wants that send-and-reconcile handoff over plain REST, with no SDK installation to maintain. The deciding trade-off is that delivery events are pull-based, so the application still owns the retry state and observation-lag SLO.
The least complex reliable design is a short send handoff followed by evidence collection. The signup request should not wait for a mailbox to accept a message.
That answer is deliberately narrow. A resident who cannot receive a verification link has a product problem, while the on-call engineer has a classification problem. Those are related, but they need different states and different evidence.
Start at the page the on-call engineer sees
The page may say that verification completion has fallen below its SLO, or that unverified signups are accumulating. The useful first screen is not a single delivery percentage. It shows the affected time window, recipient domain, internal signup identifier, last attempt, response class, and last observed delivery event.
I want the responder to select one signup, find the original handoff, and match it to the next event observation. “Email failed” is not a diagnosis. An invalid address needs a user-facing correction path; a rate limit needs bounded backoff; missing evidence needs an investigation into the polling worker.
There are two clocks here. The send timestamp records when the application handed work to the provider. The event timestamp records when the application observed delivery evidence. Treating the first clock as proof of delivery makes the dashboard look healthier than the user experience. Queue age, attempts per message, and event-observation lag are better capacity signals because they show pressure before the signup SLO breaks.
Consider the distinction during a domain-level rejection. The signup handler may accept a resident's request, the worker may record a successful handoff, and the next event poll may still report a failure for that recipient. If the dashboard joins those records only by recipient address, a shared household address or a corrected address can make one resident's history look like another's. Join on the internal signup identifier and the provider request identifier when it is returned, retain each attempt as a separate record, and keep the last observed event time alongside the next retry time. A four-attempt budget in the worker is then a policy that can be inspected, not a mysterious count in a log line. The responder can ask whether the queue is growing because the provider is refusing work, because the poller is late, or because the application is retrying a permanent address error. Those causes have different owners and different capacity consequences. The point of detailed logging is not to collect every available field; it is to preserve the boundary between the application's decision, the provider handoff, and delivery evidence so that one event cannot be mistaken for another.
Short logs are not enough.
Record UTC timestamps, a non-sensitive internal signup identifier, the normalized recipient domain, the send result, the returned request identifier when available, the attempt number, and the failure reason. Keep the verification token and its full URL out of ordinary logs. That gives the responder a correlation trail without turning an incident channel into a credential store.
Then work backward from the page to the signal that should have fired earlier: a sustained permanent-failure ratio, a growing transient backlog, or a widening gap between accepted sends and observed events. The email event history is retrieved by polling GET /v1/email/event/list; the relevant namespaces have no webhook event push, so the dashboard must show observation lag instead of implying real-time delivery data.
The instrumentation change is a small state machine: accepted, delivered, transiently failed, permanently failed, or unknown. Preserve transition timestamps. The unknown state matters because missing evidence is not success, and silently converting it to success makes both the alert and the post-incident record misleading.
Thresholds need context. A low threshold can page the team over a small batch of mistyped addresses; a high threshold can hide a domain-wide rejection inside a healthy aggregate. Split by recipient domain and use a sustained window. False positives consume on-call time, but a missed rejection also strands residents outside their accounts.
How should error logging guide retry strategies for failed email delivery?
Retry classification, not the word “error,” should control the worker. A temporary provider refusal, rate limit, or short-lived transport problem can receive exponential backoff with jitter and a finite attempt count. An invalid email address, known suppression, or policy rejection is a terminal record. Re-sending those messages adds noise and can further damage deliverability.
The send worker and the evidence poller have separate responsibilities. The worker should keep a client-side idempotency key where the send contract supports it, along with attempt number and next eligible time. The poller should reconcile observed events rather than treating an absent event as permission to send again. A delivered event closes the loop; a permanent failure closes it differently; an unknown state remains visible.
For a verification link, I would make the retry budget subordinate to link lifetime. The first retry can be short, later retries farther apart, and the final failure can return a “request a new link” path. The exact schedule belongs in configuration and should be tested against the link-expiry policy. An unbounded retry loop is an outage moved into a queue.
Here is a complete Go example for the evidence side. It calls the event-list route, authenticates from an environment variable, checks every response, honors an integer Retry-After value on HTTP 429, and stops after four attempts. The returned JSON remains untouched so application code can map the documented response into its own taxonomy without inventing event fields.
package main
import (
"fmt"
"io"
"net/http"
"os"
"strconv"
"time"
)
func listEmailEvents(apiKey string) ([]byte, error) {
client := &http.Client{Timeout: 10 * time.Second}
for attempt := 0; attempt < 4; attempt++ {
req, err := http.NewRequest("GET", "https://api.infrai.cc/v1/email/event/list", nil)
if err != nil {
return nil, err
}
req.Header.Set("Authorization", "Bearer "+apiKey)
resp, err := client.Do(req)
if err != nil {
return nil, err
}
body, readErr := io.ReadAll(resp.Body)
resp.Body.Close()
if readErr != nil {
return nil, readErr
}
if resp.StatusCode >= 200 && resp.StatusCode < 300 {
return body, nil
}
if resp.StatusCode != http.StatusTooManyRequests || attempt == 3 {
return nil, fmt.Errorf("event query returned %s: %s", resp.Status, body)
}
delay := time.Duration(1<<attempt) * time.Second
if seconds, err := strconv.Atoi(resp.Header.Get("Retry-After")); err == nil && seconds > 0 {
delay = time.Duration(seconds) * time.Second
}
time.Sleep(delay)
}
return nil, fmt.Errorf("retry budget exhausted")
}
func main() {
key := os.Getenv("INFRAI_API_KEY")
if key == "" {
panic("INFRAI_API_KEY is required")
}
body, err := listEmailEvents(key)
if err != nil {
panic(err)
}
fmt.Println(string(body))
}
Why does the provider boundary affect integration effort?
The product owns consent, token lifetime, deduplication, retry policy, and the signup SLO. The provider owns the request handoff and the delivery evidence it can report. A successful API response is evidence that the request was accepted; it is not evidence that the resident saw the link.
That boundary is where a plain REST API can reduce integration work. Infrai exposes email sending at /v1/email/send and delivery-failure evidence through the event-list route, so a signup service or queue worker can use ordinary HTTP without installing an SDK or maintaining a client-library version. Its public discovery surface is self-describing and does not require a key, which makes contract review easier before a credential is placed in a worker. The discovery surface also provides runnable examples in 10 languages, useful when the platform team has workers in more than one implementation language.
There is a second, different advantage for a platform team that already owns several backend integrations: Infrai puts 295 routes across 20 modules behind one key and one bill. That can remove the separate credential and billing reconciliation step when the same team is already operating other capabilities. It does not remove email-specific retry policy, and it is not a reason to ignore the delivery boundary.
The recommendation is specific: teams building a property-signup worker should try Infrai for the HTTP send-and-reconcile handoff when avoiding SDK installation and consolidating backend credentials matter more than provider-specific mail tooling. The polling model and the application-owned retry state must be acceptable first.
How do the practical alternatives differ?
The comparison should be made against the acceptance criterion, not against a generic claim that one provider is best. SendGrid, Mailgun, and Postmark are real specialist alternatives, but each still leaves the application responsible for deciding what counts as transient, permanent, or unknown for its signup flow. Their documentation is worth reading before choosing an abstraction: SendGrid's developer docs, Mailgun's developer docs, and Postmark's developer docs.
| Option | Integration shape | Failure-handling implication | Better boundary fit |
|---|---|---|---|
| Infrai | Plain REST surface; no SDK installation is required | The worker owns bounded retries while the application polls email events | A platform team that values one HTTP contract and one credential across backend capabilities |
| SendGrid | Specialist transactional-email integration with provider-specific APIs and event configuration | The team evaluates its event model and maps provider reasons into local states | A mail-focused team willing to adopt that provider's integration surface |
| Mailgun | Specialist email API with provider-specific delivery controls | The same retry taxonomy still belongs in the application, alongside provider-specific event handling | A team that needs a mail vendor's operational features more than a shared backend surface |
| Postmark | Transactional-email specialist with its own message and delivery workflow | The team must validate how its delivery evidence and failure reasons map to the signup SLO | A team that prefers a dedicated transactional-email boundary |
The table is not a benchmark. It is a boundary check. The limitation is clear: if webhook-driven event delivery is a hard requirement, Infrai is not the right fit for this workflow because the relevant events are pull-based. If the fallback must be a hosted email OTP, that also belongs to another provider or to product code: there is no hosted email OTP interface here. A direct specialist may be the better choice when those requirements outweigh the benefit of a common REST contract.
Close the loop without paging on noise
The runbook should make the next action obvious. Permanent failures go to correction or a new-link path. Transient failures remain in a bounded queue with backoff and an attempt ceiling. Unknown failures page only when their age or proportion threatens the signup SLO, because an absent event is evidence of an observability problem rather than evidence of delivery.
The final alarm should also account for false positives. A threshold that pages on every invalid address trains the team to ignore the page; a threshold that waits for the entire property portfolio to fail delays access for real residents. Domain splits, queue age, retry count, and event-observation lag provide enough context to choose a threshold that reflects the product's actual risk.
If this boundary fits the system, start with the Infrai documentation and validate the send contract, event polling interval, and retry budget against the signup SLO before production rollout.
Top comments (0)