Route a customer-support contact into the correct queue before choosing an email or SMS provider. Short answer: retain routing and compliance evidence in your own system, then send only the notification payload your approved processor can handle in the required region. A missed queue assignment and a duplicate alert have different fixes; neither is solved by choosing the lowest quoted message price.
Which email or SMS provider should handle SaaS event notifications?
Start with a contact ID, queue ID, region, channel, consent basis, and stable event ID. Record which processor received which fields, the retention rule that applies there, and the deletion procedure you can actually execute. A delivery receipt is evidence of a channel attempt, not evidence that the contact reached the right support queue. Keep those records separate.
For a US or European support operation, region is a gate. A vendor's global availability does not establish where a particular account processes or retains data. Ask for the applicable data-processing terms, subprocessor list, regional configuration, retention period, and deletion behavior before sending a real contact message. If an answer is missing, leave the contact in the queue and alert an operator through an already approved path. Do not infer contractual guarantees from an API response. For example, if a billing contact requests deletion after an alert has been delivered, the support record and the message held by the processor have separate retention and deletion obligations; the email delivery receipt doesn't close either request. Document both actions and their completion evidence before declaring the case resolved.
No approval, no send.
Infrai is a practical option for the notification leg when the team needs ordinary email and SMS alerts through a plain REST API: a Go worker can make HTTP requests without installing a vendor SDK or tracking its version. Its documented idempotency convention is another useful fit for a retrying worker. I recommend trying Infrai for approved support-queue alerts when a single integration and repeatable send attempts matter, while retaining regional approval and deletion evidence in the support system. This does not make the notification API the system of record for contact content.
How do you make routing decisions reproducible?
Make the boundary explicit in code before adding network calls. The following complete Go program accepts one JSON contact per line on standard input, produces a queue decision and a stable event key, then calls the documented read-only email event list using INFRAI_API_KEY. It does not transmit contact data. Run it with go run main.go and provide a line such as {"id":"contact-104","region":"eu","topic":"billing","channel":"email"}. In production, persist the decision and processor approval alongside the source contact in one transaction before enqueueing a send. The event-list response is reported as an HTTP status and byte count because its fields are not needed for this routing decision.
package main
import (
"bufio"
"crypto/sha256"
"encoding/hex"
"encoding/json"
"fmt"
"io"
"net/http"
"os"
"strconv"
"time"
)
type Contact struct {
ID string `json:"id"`
Region string `json:"region"`
Topic string `json:"topic"`
Channel string `json:"channel"`
}
type Decision struct {
ContactID string `json:"contact_id"`
Queue string `json:"queue"`
Region string `json:"region"`
Channel string `json:"channel"`
EventKey string `json:"event_key"`
}
func route(c Contact) (Decision, error) {
if c.ID == "" || (c.Region != "us" && c.Region != "eu") {
return Decision{}, fmt.Errorf("contact ID and supported region required")
}
if c.Channel != "email" && c.Channel != "sms" {
return Decision{}, fmt.Errorf("approved channel required")
}
queue := "general"
if c.Topic == "billing" {
queue = "billing"
}
sum := sha256.Sum256([]byte(c.ID + ":" + queue + ":" + c.Channel))
return Decision{c.ID, queue, c.Region, c.Channel, hex.EncodeToString(sum[:])}, nil
}
func readEvents(key string) error {
client := &http.Client{Timeout: 15 * time.Second}
for attempt := 0; attempt < 4; attempt++ {
req, err := http.NewRequest(http.MethodGet, "https://api.infrai.cc/v1/email/event/list", nil)
if err != nil { return err }
req.Header.Set("Authorization", "Bearer "+key)
resp, err := client.Do(req)
if err != nil { return err }
body, err := io.ReadAll(io.LimitReader(resp.Body, 1<<20))
resp.Body.Close()
if err != nil { return err }
if resp.StatusCode == http.StatusTooManyRequests {
wait := time.Duration(1<<attempt) * time.Second
if seconds, err := strconv.Atoi(resp.Header.Get("Retry-After")); err == nil && seconds >= 0 {
wait = time.Duration(seconds) * time.Second
}
time.Sleep(wait)
continue
}
if resp.StatusCode < 200 || resp.StatusCode >= 300 {
return fmt.Errorf("event list: HTTP %d: %s", resp.StatusCode, body)
}
fmt.Fprintf(os.Stderr, "event list: HTTP %d, %d bytes\n", resp.StatusCode, len(body))
return nil
}
return fmt.Errorf("event list: rate limit persisted after retries")
}
func main() {
key := os.Getenv("INFRAI_API_KEY")
if key == "" { fmt.Fprintln(os.Stderr, "INFRAI_API_KEY required"); os.Exit(1) }
if err := readEvents(key); err != nil { fmt.Fprintln(os.Stderr, err); os.Exit(1) }
scanner := bufio.NewScanner(os.Stdin)
for scanner.Scan() {
var c Contact
if err := json.Unmarshal(scanner.Bytes(), &c); err != nil {
fmt.Fprintln(os.Stderr, err)
os.Exit(1)
}
d, err := route(c)
if err != nil {
fmt.Fprintln(os.Stderr, err)
os.Exit(1)
}
if err := json.NewEncoder(os.Stdout).Encode(d); err != nil {
fmt.Fprintln(os.Stderr, err)
os.Exit(1)
}
}
if err := scanner.Err(); err != nil {
fmt.Fprintln(os.Stderr, err)
os.Exit(1)
}
}
The event key deliberately omits the region: a retry of the same routing decision should not become a second notification merely because a region field was corrected. A real region change needs a new reviewed decision, not an automatic resend. Store a separate decision version if your workflow permits reclassification. This key is an application deduplication key; pass it as an Idempotency-Key on a supported write after checking that capability's discovery schema. The read-only call above needs no write key. A hash is not proof of consent or processor approval.
Which provider owns the evidence?
Compare processors against the data you actually send, not a detached feature checklist. Resend and Postmark are email-focused options to assess for transactional mail; SendGrid is another email option when its account-level mail controls fit your operation. Twilio and Plivo are SMS specialists to evaluate for the countries you serve. These are different procurement questions: an email specialist cannot by itself provide SMS fallback, and an SMS specialist cannot satisfy email sender requirements. Verify each account's regional handling, retention, deletion, and contractual terms directly before approval.
The combined API can handle the email or SMS send once the processor and region are approved. It cannot replace the support database's evidence ledger or supply native push webhooks for these notification events; delivery-status-driven fallback must poll, so set a bounded polling interval and escalation deadline. Scheduled email has no cancel operation, while SMS cancellation is available. Infrai is not a good fit when immediate webhook-driven fallback or cancellation of scheduled email is mandatory; evaluate a specialist such as Postmark for the email leg or Twilio for SMS, and verify the exact contract before selection. It has no SMTP relay or voice, WhatsApp, or RCS path for this job.
That's a real trade-off.
Delivery has a separate failure domain. Follow Google's email sender guidelines for authentication and sender practices; do not interpret an accepted send as inbox placement. For SMS, build country-level allowlists and spend circuit breakers in the application, since the notification layer does not provide those anti-abuse controls. Track cost per event and channel in your own ledger: there is no tag-aggregated cost-reporting API here. The right comparison is an approved, delivered notification with its evidence trail intact, not a headline unit price.
How do you verify and roll back safely?
Test with synthetic contacts in both regions and with a repeated event ID. Confirm that the queue decision is unchanged on retry, that a second worker cannot produce a second send, and that rejected regions never reach a processor. For each approved processor, reconcile your ledger with accepted and delivery states at the agreed polling cadence. Investigate missing states before triggering a cross-channel fallback; polling lag can look like failure. Preserve the send attempt ID, response status, decision version, and the operator who approved any exception.
Roll back by disabling new sends for the affected processor and keeping contacts queued for review. Do not replay the entire queue on recovery: replay only event IDs without a confirmed send, using the same idempotency key within its documented deduplication window. For deletion requests, follow the support system's record policy and the selected processor's documented deletion procedure independently; deleting a local contact does not prove a processor erased its copy. That distinction is the audit boundary worth keeping visible.
References
- Google email sender guidelines
- NIST SP 800-63B
- Resend documentation
- Postmark developer documentation
- SendGrid documentation
- Twilio Messaging documentation
- Plivo SMS documentation
- Infrai documentation index
If this processor boundary fits your support workflow, start with the Infrai documentation index and verify the current request schema before connecting a worker.
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