Returns delivery, engagement, and deliverability counts grouped by recipient mailbox provider (for example `gmail`, `yahoo`, `microsoft`, `apple`) -- the deliverability-by-inbox-provider view. Use this to compare how each major inbox provider treats your mail, for example to spot a delivered-rate dip or complaint spike at one provider before it spreads. The values are lowercased classifier buckets, matching the `mailbox_provider` field in each row. Per-provider attribution begins only after the receiving mail system reports an outcome, so each row covers post-delivery lifecycle stages: `accepted`, `processed`, and `rejected` counts and the processing-latency percentile are not included (a recipient's mailbox provider is unknown at send time). Volume per provider is therefore attempted (`delivered + bounced`), not send-time targeted. Rows are computed against event time (not send time). Rows are ranked by the `sort` metric (default `delivered`) descending and capped at the requested `limit` (default 50, hard maximum 200). The `delivery` and `total` latency percentiles are computed across deliveries to each provider and are null if no deliveries occurred for that provider in the period. The maximum window is 365 days; requesting a longer range returns 422. Start date (inclusive) in YYYY-MM-DD, interpreted as a calendar day in `timezone` (a UTC day when `timezone` is omitted). Defaults to 30 days before `to` when omitted; with `include_trend=true` and `trend_grain=hourly` the default tightens to 29 days before `to`, keeping the defaulted window within the 720-hour trend cap. End date (inclusive) in YYYY-MM-DD, interpreted as a calendar day in `timezone` (a UTC day when `timezone` is omitted). Defaults to today in that timezone when omitted. Window may not exceed 365 days. IANA timezone identifier (for example `Asia/Kathmandu` or `America/New_York`) to report the statistics in. It is the single source of timezone: day and hour boundaries, and the relative window defaults used when `from` and `to` are omitted, are computed in this timezone instead of UTC, so a timezone with a sub-hour offset (such as India at +05:30 or Nepal at +05:45) still gets correct local-day and local-hour totals. When it is set, a `from` or `to` given as a calendar day names a local day in this timezone, and one given as an instant stays an absolute point in time but is rounded down to its hour and bucketed in this timezone (so the hour boundaries are local, not UTC). To avoid specifying the zone twice, a `from` or `to` that carries its own numeric UTC offset (for example `+05:45`) is rejected when `timezone` is set; use a calendar day or a `Z` (UTC) instant instead. Defaults to UTC. Email statistics are aggregated across all categories. Per-category filtering is not yet available; supplying this parameter returns 422. Metric to rank rows by, applied descending. Any count or rate in the response may be used; rows whose rate is undefined (zero denominator) sort last. Defaults to `delivered`. The pre-delivery metrics (`processed`, `rejected`) and `oob_bounces` are not available for this breakdown, because a recipient's mailbox provider is unknown until after delivery. Maximum number of mailbox-provider rows to return, ranked by the `sort` field descending. When true, each row also carries a `trend` array: a short per-bucket series of that provider's delivery and engagement rates over the window. Returned only when `limit` is 50 or fewer and the window is at most 90 days (trend_grain=daily) or 720 hours (trend_grain=hourly); a larger request returns 422. When `from` is omitted and `trend_grain=hourly`, the default window is 30 days (720 hours), so a request built entirely from defaults always fits the cap. Bucket grain for the `trend` series. Has no effect unless `include_trend=true`. Inclusive start date the response covers (YYYY-MM-DD). Inclusive end date the response covers (YYYY-MM-DD). 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 is near-real-time but not live; use this field to label data freshness (for example "as of 14:03") rather than assuming the numbers are to-the-second. Null when the freshness boundary is not being reported. Mailbox-provider breakdown rows, ranked by the `sort` metric (default `delivered`) descending. Empty when no eligible activity occurred in the period. The recipient mailbox provider this row aggregates, as a lowercased classifier bucket (e.g. `gmail`, `yahoo`, `microsoft`, `apple`). The set is open and grows as new providers are categorised. Distinct recipients whose message the receiving mail server accepted. Distinct recipients whose delivery failed. Approximately the sum of the five `bounces.*` sub-counts (hard, soft, admin, block, undetermined); the totals are computed independently so they may differ slightly at the approximation error. Distinct recipients who reported the message as spam. Distinct recipients in transient delivery deferral that is still being retried. Distinct recipients with a permanent delivery failure (invalid address or non-existent domain). Distinct recipients with a transient delivery failure (mailbox full or server temporarily unavailable). Distinct recipients bounced by an upstream policy block (relaying denied, blocklisted domain). Distinct recipients bounced because the receiving mail server blocked the sending IP for reputation reasons. Distinct recipients bounced where the receiving server's response did not allow precise classification. Fraction of bounced recipients that hard bounced, computed as `hard / bounced`. Null when `bounced` is zero. Fraction of bounced recipients that soft bounced, computed as `soft / bounced`. Null when `bounced` is zero. Fraction of bounced recipients that admin bounced, computed as `admin / bounced`. Null when `bounced` is zero. Fraction of bounced recipients that block bounced, computed as `block / bounced`. Null when `bounced` is zero. Fraction of bounced recipients with undetermined classification, computed as `undetermined / bounced`. Null when `bounced` is zero. Share of attempted recipients on this mailbox provider that were delivered, computed as `delivered / (delivered + bounced)`. Null when `delivered + bounced` is zero (no attempts). Share of attempted recipients on this mailbox provider that bounced, computed as `bounced / (delivered + bounced)`. Null when `delivered + bounced` is zero (no attempts). Share of delivered recipients on this mailbox provider who reported the message as spam, computed as `complained / delivered`. Null when `delivered` is zero. 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). 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. Distinct recipients who opened at least once, including opens auto-fetched by inbox privacy features. 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. Distinct click events, counting repeat clicks from the same recipient. Distinct recipients who clicked at least once. Distinct unsubscribe events, recorded via the list-unsubscribe header or the footer link. Distinct non-prefetched openers relative to recipients delivered in the same scope, computed as `unique_opens_non_prefetched / 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 `delivery.delivered` is zero. Distinct clickers relative to recipients delivered in the same scope, computed as `unique_clicks / delivery.delivered`. Clicks are attributed by event time, so engagement earned by earlier deliveries can push the rate above 1. Null when `delivery.delivered` is zero. Unsubscribes relative to recipients delivered in the same scope, computed as `unsubscribes / delivery.delivered`. Unsubscribes are attributed by event time, so the rate can exceed 1. Null when `delivery.delivered` is zero. p50, p95, and p99 latency percentiles in milliseconds for one latency family over the bucket. Percentiles are approximate (computed from a high-volume aggregation pipeline). All three are null together when no qualifying event contributed a latency measurement in the bucket. Median (50th percentile) latency in milliseconds. Null when no qualifying event contributed a measurement. 95th percentile latency in milliseconds. Null when no qualifying event contributed a measurement. 99th percentile latency in milliseconds. Null when no qualifying event contributed a measurement. p50, p95, and p99 latency percentiles in milliseconds for one latency family over the bucket. Percentiles are approximate (computed from a high-volume aggregation pipeline). All three are null together when no qualifying event contributed a latency measurement in the bucket. Median (50th percentile) latency in milliseconds. Null when no qualifying event contributed a measurement. 95th percentile latency in milliseconds. Null when no qualifying event contributed a measurement. 99th percentile latency in milliseconds. Null when no qualifying event contributed a measurement. Per-bucket rate series for this mailbox provider over the window. Present only when `include_trend=true`. The day (YYYY-MM-DD) or hour (ISO 8601, on the hour) this point covers, matching the requested `trend_grain`. Delivered recipients in this bucket. Bounced recipients in this bucket. Delivery rate for this bucket, as a fraction. Null when nothing was delivered or bounced. Bounce rate for this bucket, as a fraction. Null when nothing was delivered or bounced. Complaint rate for this bucket, as a fraction; event-time attribution can push it above 1 when complaints outrun the bucket's deliveries. Null when nothing was delivered in the bucket. On a sending-IP row complaints are not attributed to the IP, so this reads 0 in buckets that had deliveries and null in buckets that had none. Open rate for this bucket, as a fraction; event-time attribution can push it above 1 when opens outrun the bucket's deliveries. Null when nothing was delivered in the bucket. On a sending-IP row engagement is not attributed to the IP, so this reads 0 in buckets that had deliveries and null in buckets that had none. Click rate for this bucket, as a fraction; event-time attribution can push it above 1 when clicks outrun the bucket's deliveries. Null when nothing was delivered in the bucket. On a sending-IP row engagement is not attributed to the IP, so this reads 0 in buckets that had deliveries and null in buckets that had none. Total number of distinct mailbox providers with activity in the period, regardless of `limit`. When it exceeds the number of rows returned, the ranking was capped; raise `limit` (up to 200) or narrow the window to see more.