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Get mailbox email statistics

GET
/v1/email/mailboxes/{mailbox_id}/stats
const stats = await bird.email.mailboxes.stats("mbx_01abc");
console.log(stats.summary?.sends_accepted);
Response200
{
  "period": {
    "from": "2026-05-01",
    "to": "2026-05-31",
    "grain": "day",
    "data_as_of": "2026-05-25T14:03:10Z"
  },
  "summary": {
    "sends_accepted": 231,
    "delivery": {
      "accepted": 14820,
      "processed": 14810,
      "delivered": 14720,
      "bounced": 90,
      "bounces": {
        "hard": 12410,
        "soft": 14290,
        "admin": 410,
        "block": 920,
        "undetermined": 80,
        "hard_rate": 0.454,
        "soft_rate": 0.523,
        "admin_rate": 0.015,
        "block_rate": 0.0337,
        "undetermined_rate": 0.0029
      },
      "complained": 3,
      "deferred": 14,
      "rejected": 10,
      "oob_bounces": 2,
      "effective_delivered": 14718,
      "all_bounces": 92,
      "oob_rate": 0.00014,
      "delivery_rate": 0.9939,
      "bounce_rate": 0.0061,
      "complaint_rate": 0.0002
    },
    "engagement": {
      "opens": 5420,
      "opens_non_prefetched": 3210,
      "unique_opens": 3640,
      "unique_opens_non_prefetched": 2480,
      "clicks": 924,
      "unique_clicks": 621,
      "unsubscribes": 12,
      "open_rate": 0.1683,
      "click_rate": 0.0422,
      "unsubscribe_rate": 0.0009
    },
    "latency": {
      "processing": {
        "p50_ms": 420,
        "p95_ms": 1820,
        "p99_ms": 4920
      },
      "delivery": {
        "p50_ms": 420,
        "p95_ms": 1820,
        "p99_ms": 4920
      },
      "total": {
        "p50_ms": 420,
        "p95_ms": 1820,
        "p99_ms": 4920
      }
    },
    "received": 519
  },
  "data": [
    {
      "bucket": "2026-07-21",
      "sends_accepted": 12,
      "delivery": {
        "accepted": 14820,
        "processed": 14810,
        "delivered": 14720,
        "bounced": 90,
        "bounces": {
          "hard": 12410,
          "soft": 14290,
          "admin": 410,
          "block": 920,
          "undetermined": 80,
          "hard_rate": 0.454,
          "soft_rate": 0.523,
          "admin_rate": 0.015,
          "block_rate": 0.0337,
          "undetermined_rate": 0.0029
        },
        "complained": 3,
        "deferred": 14,
        "rejected": 10,
        "oob_bounces": 2,
        "effective_delivered": 14718,
        "all_bounces": 92,
        "oob_rate": 0.00014,
        "delivery_rate": 0.9939,
        "bounce_rate": 0.0061,
        "complaint_rate": 0.0002
      },
      "engagement": {
        "opens": 5420,
        "opens_non_prefetched": 3210,
        "unique_opens": 3640,
        "unique_opens_non_prefetched": 2480,
        "clicks": 924,
        "unique_clicks": 621,
        "unsubscribes": 12,
        "open_rate": 0.1683,
        "click_rate": 0.0422,
        "unsubscribe_rate": 0.0009
      },
      "latency": {
        "processing": {
          "p50_ms": 420,
          "p95_ms": 1820,
          "p99_ms": 4920
        },
        "delivery": {
          "p50_ms": 420,
          "p95_ms": 1820,
          "p99_ms": 4920
        },
        "total": {
          "p50_ms": 420,
          "p95_ms": 1820,
          "p99_ms": 4920
        }
      },
      "received": 34
    }
  ]
}

Returns the mailbox's sent and received email statistics over a time window: a period-wide summary plus a bucketed series. Sent-mail metrics have the same delivery, engagement, and latency breakdowns as the email stats endpoints. received counts mail that arrived at the mailbox.

Rows are bucketed by the time the event happened rather than the time the message was sent, so engagement that arrived during the period for a message sent earlier is counted here. Statistics start when the mailbox starts sending and receiving; the mailbox's all-time message_count and thread_count live on the mailbox resource itself.

from and to accept either calendar days (YYYY-MM-DD, day granularity only) or RFC 3339 instants (hour granularity only). Both bounds must use the same form. Window caps depend on granularity: 365 days at day, 30 days at hour. Set timezone to report in a local zone instead of UTC.

Parameters

mailbox_idstring

Mailbox identifier. Starts with mbx_.

Query Parameters

fromstring

Inclusive start of the window: a calendar day (YYYY-MM-DD, day granularity only) or an RFC 3339 instant rounded down to the hour (hour granularity only). Interpreted in timezone, or in UTC when timezone is omitted. A numeric UTC offset is rejected when timezone is set; use a calendar day or a Z (UTC) instant. Must use the same form as to. Defaults to 30 days before to at day granularity and 7 days before to at hour, when omitted.

tostring

Inclusive end of the window: a calendar day (YYYY-MM-DD, day granularity only) or an RFC 3339 instant rounded down to the hour (hour granularity only). Interpreted in timezone, or in UTC when timezone is omitted. A numeric UTC offset is rejected when timezone is set; use a calendar day or a Z (UTC) instant. Must use the same form as from. Defaults to today (day) or the current hour (hour) in that timezone when omitted. Window may not exceed 365 days at day or 30 days at hour granularity.

timezonestring

IANA timezone identifier used to group statistics, for example Asia/Kathmandu. The default is UTC. Day and hour boundaries, including the default window when from and to are omitted, follow this timezone. When this parameter is set, pass from and to as calendar days or Z instants instead of timestamps with explicit UTC offsets.

granularitystring

Granularity of the series: day (default) or hour. Echoed back as period.grain.

Possible values: day, hour

Response Payload

period
object
required

The window and bucket grain the response covers, echoed from the request, plus the freshness boundary the data is current to.

Show child attributes
period.from
string
required

Inclusive start of the window. A calendar day (YYYY-MM-DD, in the requested timezone) on the day grain. On the hour grain, an RFC 3339 UTC instant marking the start of the first hour bucket, which falls on a local hour boundary when timezone is set.

period.to
string
required

Inclusive end of the window. A calendar day (YYYY-MM-DD, in the requested timezone) on the day grain. On the hour grain, an RFC 3339 UTC instant marking the start of the last hour bucket, which falls on a local hour boundary when timezone is set.

period.grain
string
required

The bucket grain of the series, either day or hour.

Possible values: day, hour

period.data_as_of
nullable string

The instant the statistics in this response are current to: events recorded up to roughly this time are reflected, while more recent events may not be yet. Statistics are served from a rolling aggregation that refreshes every few seconds, so a response reflects data from up to a few seconds ago. Use this field to label data freshness rather than assuming the numbers are to-the-second. Null when the freshness boundary is not being reported.

summary
object
required

Single-row aggregate of the mailbox's email activity across the full requested period. Counts use each field's message, recipient, or event identity across the whole window. Repeat opens, clicks, and unsubscribes from the same recipient contribute as separate events; unique engagement fields count distinct recipients. Adding per-bucket distinct counts can overstate the summary. Latency percentiles are computed across the whole period. Rates are null when their denominator is zero.

Show child attributes
summary.sends_accepted
integer
required

Distinct email messages the mailbox sent that were accepted, counted once at the message level across the period.

summary.delivery
object
required
Show child attributes
summary.delivery.accepted
integer

Distinct recipients accepted for delivery after suppression filtering. Reported on time buckets and the period summary. Breakdown rows leave it out, because their rollups do not have it.

summary.delivery.processed
integer
required

Distinct recipients whose message was processed and handed off for delivery.

summary.delivery.delivered
integer
required

Distinct recipients whose message the receiving mail server accepted.

summary.delivery.bounced
integer
required

Distinct recipients whose delivery failed. This is approximately the sum of the five bounces.* sub-counts (hard, soft, admin, block, undetermined). The two totals are worked out independently, so they can differ slightly.

summary.delivery.bounces
object
required
Show child attributes
summary.delivery.bounces.hard
integer
required

Distinct recipients with a permanent delivery failure (invalid address or non-existent domain).

summary.delivery.bounces.soft
integer
required

Distinct recipients with a transient delivery failure (mailbox full or server temporarily unavailable).

summary.delivery.bounces.admin
integer
required

Distinct recipients refused by a policy at the receiving end, such as relaying denied or a blocklisted domain.

summary.delivery.bounces.block
integer
required

Distinct recipients bounced because the receiving mail server blocked the sending IP for reputation reasons.

summary.delivery.bounces.undetermined
integer
required

Distinct recipients bounced where the receiving server's response did not allow precise classification.

summary.delivery.bounces.hard_rate
nullable number
required

Fraction of bounced recipients that hard bounced, computed as hard / bounced. Null when bounced is zero.

summary.delivery.bounces.soft_rate
nullable number
required

Fraction of bounced recipients that soft bounced, computed as soft / bounced. Null when bounced is zero.

summary.delivery.bounces.admin_rate
nullable number
required

Fraction of bounced recipients that admin bounced, computed as admin / bounced. Null when bounced is zero.

summary.delivery.bounces.block_rate
nullable number
required

Fraction of bounced recipients that block bounced, computed as block / bounced. Null when bounced is zero.

summary.delivery.bounces.undetermined_rate
nullable number
required

Fraction of bounced recipients with undetermined classification, computed as undetermined / bounced. Null when bounced is zero.

summary.delivery.complained
integer
required

Distinct recipients who reported the message as spam via a feedback loop.

summary.delivery.deferred
integer
required

Distinct recipients whose delivery the receiving server temporarily delayed and is still being retried.

summary.delivery.rejected
integer
required

Distinct recipients rejected before any delivery attempt. Includes recipients on the workspace suppression list, transmissions that could not be completed, message-generation failures, and recipients refused by sending policy. The per-recipient rejection_reason field on GET /v1/email/messages/{message_id}/recipients surfaces the specific cause.

summary.delivery.oob_bounces
integer
required

Out-of-band bounce events: distinct failure notifications received after the receiving server had initially confirmed delivery. The count represents deduplicated events rather than unique recipients.

summary.delivery.effective_delivered
integer
required

Recipients who remain delivered after all bounce signals resolve, computed as delivered - oob_bounces. Use this as the base for engagement-rate denominators. Clamped to 0 when oob_bounces exceeds delivered.

summary.delivery.all_bounces
integer
required

Total recipients in this scope who did not receive the message, computed as bounced + oob_bounces.

summary.delivery.oob_rate
nullable number
required

Share of this scope's delivery attempts that resulted in an out-of-band bounce, computed as oob_bounces / (delivered + bounced). Null when there were no attempts.

summary.delivery.delivery_rate
nullable number
required

Share of this scope's delivery attempts that remained delivered after all bounce signals, computed as effective_delivered / (delivered + bounced). Null when there were no attempts.

summary.delivery.bounce_rate
nullable number
required

Share of this scope's delivery attempts that ultimately failed (inband or out-of-band), computed as all_bounces / (delivered + bounced). Because oob_bounces counts events rather than recipients, all_bounces can exceed the attempt count. The rate is clamped to 1. Null when there were no attempts.

summary.delivery.complaint_rate
nullable number
required

Spam complaints in this scope relative to effectively delivered recipients, computed as complained / effective_delivered. Complaints are attributed by event time, so a scope can record more of them than it effectively delivered, pushing the rate above 1. Null when effective_delivered is zero.

summary.engagement
object
required
Show child attributes
summary.engagement.opens
integer
required

Distinct open events, counting repeat opens from the same recipient and opens auto-fetched by inbox privacy features (such as Apple Mail Privacy Protection and the Gmail image proxy).

summary.engagement.opens_non_prefetched
integer
required

Distinct open events excluding those auto-fetched by inbox privacy features. Same event-counting semantics as opens (repeat opens from the same recipient count separately), with prefetched opens removed.

summary.engagement.unique_opens
integer
required

Distinct recipients who opened at least once, including opens auto-fetched by inbox privacy features.

summary.engagement.unique_opens_non_prefetched
integer
required

Distinct recipients who opened at least once, excluding opens auto-fetched by inbox privacy features. This is the numerator used for open rate, so iOS-heavy audiences (Apple Mail Privacy Protection and similar) do not inflate it.

summary.engagement.clicks
integer
required

Distinct click events, counting repeat clicks from the same recipient.

summary.engagement.unique_clicks
integer
required

Distinct recipients who clicked at least once.

summary.engagement.unsubscribes
integer
required

Distinct unsubscribe events, recorded via the list-unsubscribe header or the footer link.

summary.engagement.open_rate
nullable number
required

Distinct non-prefetched openers relative to effectively delivered recipients in the same scope, computed as unique_opens_non_prefetched / delivery.effective_delivered; on rows without an effective_delivered field (the mailbox-provider breakdowns) the denominator equals delivery.delivered. The numerator excludes opens auto-fetched by inbox privacy features. Opens are attributed by event time, so engagement earned by earlier deliveries can push the rate above 1. Null when the denominator is zero.

summary.engagement.click_rate
nullable number
required

Distinct clickers relative to effectively delivered recipients in the same scope, computed as unique_clicks / delivery.effective_delivered (delivery.delivered on rows without an effective_delivered field). Clicks are attributed by event time, so engagement earned by earlier deliveries can push the rate above 1. Null when the denominator is zero.

summary.engagement.unsubscribe_rate
nullable number
required

Unsubscribe events relative to effectively delivered recipients in the same scope, computed as unsubscribes / delivery.effective_delivered (delivery.delivered on rows without an effective_delivered field). Unsubscribes are attributed by event time, so the rate can exceed 1. Null when the denominator is zero.

summary.latency
object
required
Show child attributes
summary.latency.processing
object

Approximate p50, p95, and p99 latency percentiles in milliseconds for one latency family over the bucket. All three are null when no qualifying event contributed a measurement.

Show child attributes
summary.latency.processing.p50_ms
nullable integer
required

Median (50th percentile) latency in milliseconds. Null when no qualifying event contributed a measurement.

summary.latency.processing.p95_ms
nullable integer
required

95th percentile latency in milliseconds. Null when no qualifying event contributed a measurement.

summary.latency.processing.p99_ms
nullable integer
required

99th percentile latency in milliseconds. Null when no qualifying event contributed a measurement.

summary.latency.delivery
object

Approximate p50, p95, and p99 latency percentiles in milliseconds for one latency family over the bucket. All three are null when no qualifying event contributed a measurement.

Show child attributes
summary.latency.delivery.p50_ms
nullable integer
required

Median (50th percentile) latency in milliseconds. Null when no qualifying event contributed a measurement.

summary.latency.delivery.p95_ms
nullable integer
required

95th percentile latency in milliseconds. Null when no qualifying event contributed a measurement.

summary.latency.delivery.p99_ms
nullable integer
required

99th percentile latency in milliseconds. Null when no qualifying event contributed a measurement.

summary.latency.total
object

Approximate p50, p95, and p99 latency percentiles in milliseconds for one latency family over the bucket. All three are null when no qualifying event contributed a measurement.

Show child attributes
summary.latency.total.p50_ms
nullable integer
required

Median (50th percentile) latency in milliseconds. Null when no qualifying event contributed a measurement.

summary.latency.total.p95_ms
nullable integer
required

95th percentile latency in milliseconds. Null when no qualifying event contributed a measurement.

summary.latency.total.p99_ms
nullable integer
required

99th percentile latency in milliseconds. Null when no qualifying event contributed a measurement.

summary.received
integer
required

Distinct emails the mailbox received, counted once across the period.

data
array of object
required

One row per bucket in the period, in chronological order. Buckets with no activity are included with zero counts.

Show child attributes
data.bucket
string
required

The day (YYYY-MM-DD) or instant (RFC 3339, on the bucket boundary) this point covers, matching the period's grain.

data.sends_accepted
integer
required

Distinct email messages the mailbox sent that were accepted in this bucket, counted at the message level (one per accepted send regardless of how many recipients it addresses). Every other sent-mail metric in delivery and engagement is recipient-level or event-level.

data.delivery
object
required
Show child attributes
data.delivery.accepted
integer

Distinct recipients accepted for delivery after suppression filtering. Reported on time buckets and the period summary. Breakdown rows leave it out, because their rollups do not have it.

data.delivery.processed
integer
required

Distinct recipients whose message was processed and handed off for delivery.

data.delivery.delivered
integer
required

Distinct recipients whose message the receiving mail server accepted.

data.delivery.bounced
integer
required

Distinct recipients whose delivery failed. This is approximately the sum of the five bounces.* sub-counts (hard, soft, admin, block, undetermined). The two totals are worked out independently, so they can differ slightly.

data.delivery.bounces
object
required
Show child attributes
data.delivery.bounces.hard
integer
required

Distinct recipients with a permanent delivery failure (invalid address or non-existent domain).

data.delivery.bounces.soft
integer
required

Distinct recipients with a transient delivery failure (mailbox full or server temporarily unavailable).

data.delivery.bounces.admin
integer
required

Distinct recipients refused by a policy at the receiving end, such as relaying denied or a blocklisted domain.

data.delivery.bounces.block
integer
required

Distinct recipients bounced because the receiving mail server blocked the sending IP for reputation reasons.

data.delivery.bounces.undetermined
integer
required

Distinct recipients bounced where the receiving server's response did not allow precise classification.

data.delivery.bounces.hard_rate
nullable number
required

Fraction of bounced recipients that hard bounced, computed as hard / bounced. Null when bounced is zero.

data.delivery.bounces.soft_rate
nullable number
required

Fraction of bounced recipients that soft bounced, computed as soft / bounced. Null when bounced is zero.

data.delivery.bounces.admin_rate
nullable number
required

Fraction of bounced recipients that admin bounced, computed as admin / bounced. Null when bounced is zero.

data.delivery.bounces.block_rate
nullable number
required

Fraction of bounced recipients that block bounced, computed as block / bounced. Null when bounced is zero.

data.delivery.bounces.undetermined_rate
nullable number
required

Fraction of bounced recipients with undetermined classification, computed as undetermined / bounced. Null when bounced is zero.

data.delivery.complained
integer
required

Distinct recipients who reported the message as spam via a feedback loop.

data.delivery.deferred
integer
required

Distinct recipients whose delivery the receiving server temporarily delayed and is still being retried.

data.delivery.rejected
integer
required

Distinct recipients rejected before any delivery attempt. Includes recipients on the workspace suppression list, transmissions that could not be completed, message-generation failures, and recipients refused by sending policy. The per-recipient rejection_reason field on GET /v1/email/messages/{message_id}/recipients surfaces the specific cause.

data.delivery.oob_bounces
integer
required

Out-of-band bounce events: distinct failure notifications received after the receiving server had initially confirmed delivery. The count represents deduplicated events rather than unique recipients.

data.delivery.effective_delivered
integer
required

Recipients who remain delivered after all bounce signals resolve, computed as delivered - oob_bounces. Use this as the base for engagement-rate denominators. Clamped to 0 when oob_bounces exceeds delivered.

data.delivery.all_bounces
integer
required

Total recipients in this scope who did not receive the message, computed as bounced + oob_bounces.

data.delivery.oob_rate
nullable number
required

Share of this scope's delivery attempts that resulted in an out-of-band bounce, computed as oob_bounces / (delivered + bounced). Null when there were no attempts.

data.delivery.delivery_rate
nullable number
required

Share of this scope's delivery attempts that remained delivered after all bounce signals, computed as effective_delivered / (delivered + bounced). Null when there were no attempts.

data.delivery.bounce_rate
nullable number
required

Share of this scope's delivery attempts that ultimately failed (inband or out-of-band), computed as all_bounces / (delivered + bounced). Because oob_bounces counts events rather than recipients, all_bounces can exceed the attempt count. The rate is clamped to 1. Null when there were no attempts.

data.delivery.complaint_rate
nullable number
required

Spam complaints in this scope relative to effectively delivered recipients, computed as complained / effective_delivered. Complaints are attributed by event time, so a scope can record more of them than it effectively delivered, pushing the rate above 1. Null when effective_delivered is zero.

data.engagement
object
required
Show child attributes
data.engagement.opens
integer
required

Distinct open events, counting repeat opens from the same recipient and opens auto-fetched by inbox privacy features (such as Apple Mail Privacy Protection and the Gmail image proxy).

data.engagement.opens_non_prefetched
integer
required

Distinct open events excluding those auto-fetched by inbox privacy features. Same event-counting semantics as opens (repeat opens from the same recipient count separately), with prefetched opens removed.

data.engagement.unique_opens
integer
required

Distinct recipients who opened at least once, including opens auto-fetched by inbox privacy features.

data.engagement.unique_opens_non_prefetched
integer
required

Distinct recipients who opened at least once, excluding opens auto-fetched by inbox privacy features. This is the numerator used for open rate, so iOS-heavy audiences (Apple Mail Privacy Protection and similar) do not inflate it.

data.engagement.clicks
integer
required

Distinct click events, counting repeat clicks from the same recipient.

data.engagement.unique_clicks
integer
required

Distinct recipients who clicked at least once.

data.engagement.unsubscribes
integer
required

Distinct unsubscribe events, recorded via the list-unsubscribe header or the footer link.

data.engagement.open_rate
nullable number
required

Distinct non-prefetched openers relative to effectively delivered recipients in the same scope, computed as unique_opens_non_prefetched / delivery.effective_delivered; on rows without an effective_delivered field (the mailbox-provider breakdowns) the denominator equals delivery.delivered. The numerator excludes opens auto-fetched by inbox privacy features. Opens are attributed by event time, so engagement earned by earlier deliveries can push the rate above 1. Null when the denominator is zero.

data.engagement.click_rate
nullable number
required

Distinct clickers relative to effectively delivered recipients in the same scope, computed as unique_clicks / delivery.effective_delivered (delivery.delivered on rows without an effective_delivered field). Clicks are attributed by event time, so engagement earned by earlier deliveries can push the rate above 1. Null when the denominator is zero.

data.engagement.unsubscribe_rate
nullable number
required

Unsubscribe events relative to effectively delivered recipients in the same scope, computed as unsubscribes / delivery.effective_delivered (delivery.delivered on rows without an effective_delivered field). Unsubscribes are attributed by event time, so the rate can exceed 1. Null when the denominator is zero.

data.latency
object
required
Show child attributes
data.latency.processing
object

Approximate p50, p95, and p99 latency percentiles in milliseconds for one latency family over the bucket. All three are null when no qualifying event contributed a measurement.

Show child attributes
data.latency.processing.p50_ms
nullable integer
required

Median (50th percentile) latency in milliseconds. Null when no qualifying event contributed a measurement.

data.latency.processing.p95_ms
nullable integer
required

95th percentile latency in milliseconds. Null when no qualifying event contributed a measurement.

data.latency.processing.p99_ms
nullable integer
required

99th percentile latency in milliseconds. Null when no qualifying event contributed a measurement.

data.latency.delivery
object

Approximate p50, p95, and p99 latency percentiles in milliseconds for one latency family over the bucket. All three are null when no qualifying event contributed a measurement.

Show child attributes
data.latency.delivery.p50_ms
nullable integer
required

Median (50th percentile) latency in milliseconds. Null when no qualifying event contributed a measurement.

data.latency.delivery.p95_ms
nullable integer
required

95th percentile latency in milliseconds. Null when no qualifying event contributed a measurement.

data.latency.delivery.p99_ms
nullable integer
required

99th percentile latency in milliseconds. Null when no qualifying event contributed a measurement.

data.latency.total
object

Approximate p50, p95, and p99 latency percentiles in milliseconds for one latency family over the bucket. All three are null when no qualifying event contributed a measurement.

Show child attributes
data.latency.total.p50_ms
nullable integer
required

Median (50th percentile) latency in milliseconds. Null when no qualifying event contributed a measurement.

data.latency.total.p95_ms
nullable integer
required

95th percentile latency in milliseconds. Null when no qualifying event contributed a measurement.

data.latency.total.p99_ms
nullable integer
required

99th percentile latency in milliseconds. Null when no qualifying event contributed a measurement.

data.received
integer
required

Distinct emails the mailbox received in this bucket.

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